AITB for pretending I don't remember this guy I went to high school with?

The last time I saw him was almost ten years ago in high school. Long story short...

In high school, I didn't want to sit next to anyone at lunch because there was no one I actually clicked with, but he kept begging me to sit next to him. Every time I would ignore him or sit somewhere else, he would keep staring at me to get my attention and pressure me to spend time with him. He might be autistic because he was never able to pick up on social cues when someone isn't interested in spending time with him and he didn't know what the hell he was doing socially sometimes. If I had an autistic friend who wasn't able to pick up on these social cues, I would've also told them to stop trying so hard. Maybe he was too handsome and popular to be diagnosed with autism. Maybe he was diagnosed with autism and he assumed I was autistic because my schizo symptoms are so similar to autism. Maybe he really was an ass because his friends were probably telling him to stop trying so hard. Maybe he wasn't autistic at all and he was just an ass. He might've had a crush on me or something because he seemed pretty obsessed with me in high school especially after he found out I'm bi. I don't even know why he would like me as a friend either. I'm a bi guy and I'm just not attracted to him at all.

Last weekend, I saw him at the mall with his friend who I also went to high school with. He said hi to me. I said "do I know you?' (pretending I don't remember him). He said 'of course we went to high school together.' I said "I don't remember you sorry." He said "of course you do, high school wasn't so long ago" and then he started bringing up all these details and accused me of pretending I don't remember him. I said "even if someone is conveniently pretending they don't remember you, it doesn't mean you need to start interrogating them because they're just going to get angry and confused about why you're not leaving them alone after they said they don't remember you." His friend said "I wish he never stuck up for you." I remember him claiming that he "sticks up for me." I never actually heard him or saw him sticking up for me when I was in the same room as him and no one ever told me anything about it either so how am I supposed to believe it's true. No one was bothering me anyways. I didn't know who to trust and who not to trust.

I said "and maybe if you were such a great friend you would've told him to stop trying so hard." His friend told me how they both argued about me. I said "good maybe he should've listened to you because you're smarter than him" and I walked away really fast.

Am I really the buttface? I wouldn't have reacted the way I reacted if he just left me alone after I said I don't remember him. I even blocked him on social media shortly after high school, so I don't know why he's still being persistent when he saw me at the mall which I assume was just a coincidence.