When Biden said "friend" I'm fairly sure he was meaning romantic partner. He talks about people in an intimate relationship taking pictures of their "friend." All of my great aunts and uncles and grandparents, who would be near Biden's age would constantly call a gf or bf just your "friend."

Biden is essentially describing revenge porn, that when you're together with someone, a lot of people end up taking some sexually explicit pictures or video of themselves or where their partner, and they're shared between the two people. The intimate relationship partners have a bad breakup and one of them threatens to start spreading these explicit pictures on the internet in order to hurt, punish, or manipulate their ex gf/bf.

I get that people are desperate for hopium, and this quote of Biden's seems kinda questionable with what's out there about him, but I do think that this is a comment on revenge porn and not him alluding to people possibly having blackmail on himself.