FTR: my daughter is also autistic. I am a teacher and I remember my schooldays very well indeed. My daughter is very pretty and has had the ‘Johnny loves Suzy’ thing too; TBH, I think most kids have.
It’s a social situation that can be awkward - it’s really not bullying. It’s usually the kind of thing done among friends; you know how friends will also be more likely to trade mild ‘yo mama’ insults that they wouldn’t with an enemy?
That makes it difficult for autistic kids to deal with, so you’re right to ask for advice about it. The best advice is to teach your son some stock phrases, like the ones suggested above, and also teach him not to be worried about it. For that, you need to not be worried about it yourself.
I understand you being worried about this sort of thing for your son; I’ve always been worried about my daughter in social situations too, and was terrified about her starting secondary (middle) school. She’s actually doing well - really well.
My daughter also used to do the inappropriate hugging thing and I think that some of the stuff her autism outreach workers did with her really helped with this - they wouldn’t tell her what to do, but share stories and lead her towards discovering the answer on her own.
They’d have a very simple scenario, like this one:
'Johnny often plays ball with Nathan at break. Nathan often passes the ball to Johnny and doesn’t get mad if he misses. Nathan is Johnny’s friend. On Friday after break, Nathan sees Johnny talking to a girl called Suzie. Nathan calls out “Johnny loves Suzie! Johnny loves Suzie!” Johnny doesn’t love Suzie - she’s just his friend - so gets very annoyed and shouts ‘I do NOT love Suzie!’
Next day at break Nathan asks Johnny to play ball again and Johnny says no. Johnny goes to look for Suzie, but she won’t talk to him.’
I think the teacher would ask something like ‘what happened next?’ and ‘let’s go back to this part of the story here, and change it so that it has a happier ending…’ And then she’d learn some stock phrases to fall back on.
Getting the teacher involved should not be one of the happier ending scenarios. The teacher would have to tell the other kids off, who would be bewildered, and not want to talk to Johnny any more in case they got in trouble again. and Johnny would be marked down as the kid who goes running to the teacher because of what really is ordinary friendly teasing. Friends do tease each other - that’s hard for autistic kids to understand, but they can, with time.
If teasing of this sort exceeded the anxiety that you felt when performing CPR on your Dad, then you need to deal with your own memories; I know you’ll be doing your best not to pass your anxiety on to your child, but I also know that it’s hard not to.
Now, if you were talking about an entire class of kids surrounding your son and chanting it whenever he appeared, that would be bullying, but that’s not what I get from your OP.