Distaste for another group's culture is close to association by race, and a group's religion is quite influential on its culture.

What is problematic is that all people who dress a certain way and have similar features are often lumped together, even if they are actually of different ethnicities.

That said, religious association should be just as protected from prejudice as ethnic prejudice should be.

Mistaking a member of a group for any member of that group is mental shorthand. Handy heuristic for activating previous knowledge. But it is an irrational leap to assume any member of a group is definitely representative of the traits you have previously gathered to be common to other members of that group, unless, of course, the trait is definitive, such as assuming any atheist believes there is no god.

An entirely separate issue is the practices of a belief system which are harmful or maladaptive, or are a root of conflict. For instance, white supremacy. The practices that grow from that belief system are harmful to others, at least generally speaking. I'm sure specific instances could be trotted out that are not hateful.

Now, so far as I can see, there is a group of people very hostile to anyone not a member of that group, and ideology is central to why that is. However, the specific strain of Islam responsible for this violent hostility is not to be confused with Islam as a whole, any more that the particular beliefs that are at the root of atheistic persecution of believers of god-affirming faiths should be taken to be representative of all those who espouse atheism.

In short, some atheist jerks are jerks because they are jerks, not because they are atheists, just as some Muslims are violent not because they are Muslim, but because they are violent. Justification by belief is not identical to application of that belief in good faith.

There is nothing inherent in Christianity that led inevitability to the crusades or to Hitler's final solution. The system of beliefs and the power to sway others inherent in a submission-encouraging ethos was borrowed by leaders and exploited. Jesus never said to do those things. Leaders who claimed to speak for Him did.

Now, Islam is admittedly different in that several passages do support hostility toward outsiders. And this is central.

Islam is more given to exploitation by leaders because of these problematic passages.

A definition of fundamental is important. We often label extremists as fundamentalists. If those who follow the written word of an ethos can be called faithful to that ethos, then they can be referred to honestly as fundamentalist. The text or core of the belief system guides their behavior.

If we take Jesus' teachings as an example, a true fundamentalist would love others, return blessings for persecution, help the poor, the fatherless and the widow, etc. But those we have labelled fundamentalists do not act this way. Indeed, they call themselves fundamentalists, but this can be shown to be disingenuous.

Similarly, the no true Scotsman fallacy asserts that anyone who claims membership in a group cannot be said to not belong to that group because their beliefs or actions are repugnant to other members of that group. Why the claim of membership is taken as gospel is a different fallacy.

What's true is that members of a group can give others a bad name.

In summary, grouping others and assuming all members of that group are the same can only be done accurately to the extent that the group is defined accurately. A rude atheist is representative of only that group of atheists who are also rude. The category of Muslims may contain violent Muslims, but the set is larger than the subset, and traits identified in the subset are not generalizable to the set as a whole.

I'm Christian, by the way, and have no problem with criticism of religion itself or of how it is practiced. Or disbelief either. Most criticisms are valid. But inaccuracies breed prejudice.

I do have criticisms myself of Islam, as it is inconsistent in ways that lend themselves to distorted practices, such as violence toward perceived outsiders. The religion itself can become a version that is definitely problematic. But as widely practiced and interpreted, it is usually not.

Christianity has its own problems, mostly due to badly-derived interpretations and applications, at least in my opinion. Inequality of men and women for a strong example, and conformity and judgmentalism.

I'm sure an insider perspective on atheism yields as many valid criticisms, as it is prey to human error as anything.

All of this is not to rebut you in any way. Rather, your point of view inspired me to go on at length about things that have been brewing in my mind for some time. Thank you in advance for your indulgence.