The only argument you seem to be adding here is that if you are convinced that you are right than everyone must agree with you. The moral argument against eating meat can never be universally right because the argument for ethical vegetarianism is based a single fundamental question. Is it okay to kill animals for food? All of the philosophical framing and calculations of net pain caused vs calories gained is just dancing around one simple question. This is a perfect example of why you can't apply a moral rule universally. We don't accept that moral argument against meat is valid it isn't. It is a theological question that can neither be proven nor disproven. You don't have knowledge that killing animals is wrong, you believe it. People who eat meat believe it is okay. You can't use the argument that animals are victims, because the people who are consuming the animals can say that their suffering does not outweigh their desire to eat them. The suffering of animals matters more to you than it does to them for purely personal reasons. Beating children is not an inherently evil act you are making a universal moral assumption. Our science has shown that children may develop better if not beaten, so we use the laws and systems of our country to encourage people not to beat their children.
No we shouldn't hold children and the mentally disabled responsible like adults. We don't allow them the full rights of adults because they don't fulfill the responsibilities. The same could be applied to animals. They are unable to understand that we don't want them to hurt each other so we don't have any obligation to extend rights (a purely human construct) to them. Animals have no concept of a right to life and I see no reason to believe they would be in favor of it if they did. Humans are not higher order being, we are the same to nature as a cow or a leopard, we have no obligation to be responsible for the well being of other animals.
The definition of what is and not a crime dictates the crime rate as much enforcement efforts do. If you want to equate meat consumption to crime than you are starting with a behavior engaged in by 99.9 % of all humans that ever lived. Any sociologist would tell you that criminalizing a behavior that prevalent would be a disaster. Do you suppose meat would be produced more ethically if it was being sold in a black market? It seems to me that the best course of action for ethical vegetarians is to live the life that feels right to them, trying to show yourselves as an example of health and happiness will likely win you more supporters than proselytizing. Trying to change someone's mind in a respectful way is a reasonable thing to do as long it isn't done in a way that causes practical problems for society. BTW causing practical problems for society is not a moral judgement. If say, vegetarians bought enough political influence to ban meat, they would be hindering societies ability to function by clogging our criminal justice system with newly appointed criminals. It is a practical problem free from morality.
I think I've made it pretty clear that I'm not arguing in support of objective morality. I don't believe that the Taliban's moral code is false, or at least any more false than any other. My point here was to illustrate why someone seeking less cruelty or suffering in the world should not deal in moral absolutism. Strong belief in absolute moral authority is how these killings are justified. It isn't an argument you want on your side if you oppose human suffering. Moral absolutes are another theological position. They can't be proven or disproven and are purely a matter of belief. This doesn't make them bad or good, but rather irrelevant. It is the practical consequences of absolute morality that are relevant. No moral views are false, nor are any right. The intensity of the emotional experience of extreme morality is relevant to understanding what the consequences may be and helps us determine if it presents a practical threat relative to our own lives.
Within the category of practical threats I'll include that it may offend the sensibilities of enough people within a society that the society may be compelled to action, but this would still be an indirect relationship to morality as it would be of practical consequence to the offended society.
If Joe wants to start killing Jews we stop him because our society has given Jews the right to be protected from murder. Joe has every right to hate Jews and want them dead, but when it comes to the practical matter of killing them he comes into conflict with the practical need for an ordered society. Joe is causing disorder which makes society less productive and reduces its viability. So it isn't Joes practical concerns that dictate what happens in this situation it is societies. Whether Joe values his freedom more than his Jew hating is irrelevant, it isn't in the practical interest of society to let Joe kill Jews. If Joe was a very powerful man with huge numbers of followers willing to commit violence for the cause of Jew hate, than there may come a time when letting Joe kill Jews is in the practical interest of society. If the society where Joe was killing Jews was a member of an even larger scale global government system than the amount of power Joe needs to get over the hump of practicality may become impossibly large.
I don't agree that moral relativism discourages tolerance in the least. Rather it is much more tolerant than objective morality because it gives no belief a higher value than any other. As long as one believes that they stand on moral high ground they are intolerant. Moral relativism doesn't allow for such high ground, rather it tolerates all moral beliefs, but discriminates on the basis of actions detrimental to the practical functioning of society. So it's not about the rightness or wrongness of what people think but rather the benefit or detriment of what they do. It may seem like an arbitrary distinction, but in my opinion it is a philosophically relevant one.
My outlook is cynical in the sense that I don't consider morality to be the driving force for human actions. In the context of the accepting that suffering is a natural condition that can exist for any being I don't agree that that outlook is cynical. I believe that suffering is neither wrong nor right, and as such I don't think that suffering is insincere, I believe it to be a natural condition and I see no benefit to my opposing it. It is no different than saying it is moral to oppose death. You can't oppose death, there is nothing to oppose. It simply is. Suffering is just a state of being not fundamentally different from any other. The only way in which suffering is undesirable is relative to a more desirable condition, but the definition of a desirable condition has the same exact weakness in that it is only desirable relative to an undesirable condition.