It's easy to see when someone has an offensive name. Of course, there are times when it's easy to see someone is griefing other players. However, we don't really have a good system in place for that. We'd need a team available to review the very high number of videos we'd receive. Not to mention the large amount of time dedicated to reviewing video of players that shouldn't be actioned. I'm sure we'd get a lot of reports that someone is cheating or griefing just because they took a loss. So, it's a use of resources that could otherwise be put back into the game, but instead would be used to make drop-ins more friendly. Would that be worth sacrificing work on the game that the community would rather have?
Also, and I get this doesn't resolve the issue, you can better avoid toxic drop-in players by only dropping in on clubs. I will back out of lobbies until I get matched with a club. The play is normally far better than a full team of randoms. I truly wish we had a better system for actioning trolling. We need to do better here. Drop-ins are an introduction to this mode for many and I'm sure some have been scared off because of those types of players. Regardless, no matter how many anti-griefing features we add or if we started taking reports for this, people will always find a way to troll. It's most likely a never ending battle.