Guarantee he is not taking actual 'legal action' as in lawsuits (which is what he means when he says prosecution, seeing as copyright infringement is a civil dispute not criminal one and he doesn't have the power to prosecute anyone regardless) , he is just using the DMCA that most platforms comply with to get them to take down posts and accounts who post his stuff, if he was filing lawsuits there would court documents from California or wherever he lives showing him trying to get people dragged into court formally which would be in the public domain.
No one sues people over OF content, you'd have to locate the person infringing your copyright among other things so it isn't worth the money it would cost to go to court which could be months of litigation and retaining lawyers ( for instance if the person was outside the US, a going to a US court would be useless to Mark) , he probably just has a PR firm or management firm/ group that is issuing DMCA takedown notices on his behalf, those notices don't even require a lawyer or ever stepping foot in a court unless the site refuses to comply. Most sites just force you to take it down then that is the end of it, unless you fight the claim which doesn't really happen regarding OF content
Here is a short vid explaining it if anyone is interested:
Long story short just don't post his content on any account you want to keep as he might get it suspended otherwise there are really no repercussions for posting his stuff
Thats it