I assume it's referring to The Sims game interactions.
When two characters would talk to each other and one of them said something that the other didn't like, then it showed a rather similar sign above their head and some status bar went down.

Friendship down

Two minus signs means the guy disliked it a lot.

https://en.wikipedia.org/wiki/The_Sims

It's the icon in The Sims for when a sim REALLY doesn't like the actions of another sim.

Too old? Dude, that's from the Sims 2.

It means one dude holding another dude's hand and gives them a massive boner.

In fact, you are too young to realize it's a 20 year old joke.

I presume “do you to be my boyfriend?”