Okay, this is going to be a long one.
You're 14. You know this, I know this. Yes, it is absolutely infuriating when someone tells you that you don't know something, can't do something, or shouldn't do something because of your age. It just makes you want to do that thing even more. However, sometimes the person telling you not to do something is right, as it is in this case. It's not because of your age that we don't take you seriously. In fact, the reason we are taking you seriously is because of your age. You do not need to be exposed to this type of thinking right now.
I know you say you have thought like this for two years. You say that you did not have friends then. I understand why you may have decided to seek out other people who felt that way too so you could feel a sort of kinship. But 4chan is not a great place to go to find that. By your own admission, they were the ones who introduced you to Elliot Rodger by calling him a hero and praising him. Nobody should think like that, let alone a 12 year old.
You know what? I read his manifesto too. Yes, it was sad. I did pity him. I pitied that he felt the way he did, that he felt lonely and unloved. I have felt this way myself. But killing innocent people? That's not how you fix anything.
What if a man like Elliot Rodgers had decided that in place of women and "chads", he hated 5 year olds and took those precious lives away from the world? Could you praise a man like that? Elliot Rodgers is no different.
Elliot Rodgers was ill. Severely ill. He had self-esteem issues, probably anxiety and depression, and I don't know what else. He didn't try and let his hatred of women and "Chads" fester until it blew up and he committed the horrible acts he did. You do not want this to happen to you.
I know you say you were not serious about wanting to kill people, but the fact that you even have those thoughts is telling and an issue in itself. 14 year olds, anyone actually, should not be thinking like that. You shouldn't have a YouTube channel idolising a man who took seven innocent lives away from this world.
Society does not consider you a loser for not having lost your virginity at age 16. Maybe it feels that way to you, and I understand that virginity and sex may be a huge deal to you right now, but to the rest of the world it isn't. I'm a virgin. I'm 20. Society doesn't consider me a loser. I know hundreds of people, guys and girls, who are still virgins at age 14 and up. You are building this up in your head. Your peers are not all running around fucking each other and then making fun of you being your back.
As for your dislike of PDA, which seems to be common amongst incels, that is something you need to work on. You should not be getting angry at two 7th graders kissing. It does not affect your life. That is just two people being happy and "loving" each other. Maybe you can feel jealous seeing that, and that's fine, but anger? No.
Yes, there are teenagers who are sexually active right now. You talk about the guy on reddit. Maybe he is sexting people at you age, maybe not. There is a chance he was lying to make himself look cool. It's the internet, people lie. Especially on a board dedicated to teenagers. It's human nature to want to impress others and look cool.