He is an idiot. But aside from the jokes, I personally don't wish federal prison on him or most people. It's a wretched existence.
Some background on Mr. 6ix9ine (his name spelling is obnoxious)...
He brags about his gang affiliations. I'm sure that factors into his street cred and popularity, but more crucial, it factors into his controversial nature. He's already been robbed once, and his crew have got into scraps with, um, street personnel at different concerts. Not a fan of his music but I see why the kids love him. That energy in his music is really hard to fake.
So the Feds got him on a RICO case, which just means that if they see you affiliating with criminals committing crimes, they can charge and convict you of those crimes if they can prove affiliation. RICO (Rackeetering Influenced and Corrupt Organizations act) laws were created to deal with organized crime in the 70s. Prior to this, mob bosses were untouchable, because they would deny knowledge of crimes their soldiers committed. Without actual evidence of an order, the soldier would take the hit but the boss would continue unscathed. RICO made it easier for the feds to get at mob bosses. Giuliani as a prosecutor used RICO laws to decimate the NY mafia in the 80s. It's a powerful tool prosecutors turn to... when there is little evidence someone actually pulled the trigger. They'll just say you were hanging out with them, so of course you were affiliated. I'd be more of a fan if they applied the same fervor to prosecuting white collar crimes using the RICO (half of Wall Street post 2008 could have been in jail). Obviously they mostly keep it for the b/h drug dealers.
Back to Mr. 6ix9ine... he is currently on probation for a sex crime, in state court. This charge puts him in a predicament. I'm sure the feds don't have much directly linking him to a crime, but with the RICO they can press on him to give up actual criminals in the gangs he affiliates with. He could do that and iron out a easy deal... but there's his street cred gone. He can decide to fight the charges in federal court. However his chances of victory are slim. The feds are very meticulous in building cases and they only bring charges they think are winnable in court, or heavy enough to persuade the defendant into pleading guilty. It's not impossible, but he will need an expensive lawyer team, and favorable bail conditions that allow him to still earn money and tour, while awaiting trial. Or have a music label back him financially, in return for a cut of future profits.
Either way, hanging out with gang members publically is bad business. He sowed the wind and is reaping the whirlwind.