As somebody who has been playing large online multiplayer video games for the last 20 years... my opinion is that, at the very least, nobody else who has tried has been successful thus far. The best indicator of future performance is past performance. You could have some sort of flagging/performance review system similar to the reporting system that Destiny already has, where you can report someone for various things. But this would probably be too easy to misuse, and it currently never seems to result in anything anyways--and probably for good reason, since a report here and there with no real evidence behind it isn't enough concrete information for Bungie to be throwing bans around.
League of Legends has gone to the most drastic lengths I've seen thus far when it comes to banning/suspending even questionable forms of "toxicity"--with the more obvious cases being based on empirical, text chat evidence--yet it's still rampant there at seemingly every level of play.
The standard practice in most Destiny LFG groups seemed to be "have the emblem that proves that you've already done what we're going to be trying to do" in order to get invited, and I expect a lot of the people who are looking for an extra body through the guided games service will continue to use that metric. Obviously this does very little for new players, nor does it do anything to prevent the people you do invite/are invited by from slinging racial epithets or generally being too stoned to avoid standing in the lava or whatever. Shit like that is never going to stop being a box of chocolates.
Groups could signal that they're willing to try and teach/carry new players through; while I'm sure you'll see some groups like that eventually, I doubt they'll really start to show up until the content has already been in the wild for a while. There are streamers out there who will carry you to the Lighthouse if you've never been there before, and I'm sure there will be people who will carry you to the end of a raid. But in terms of maximizing that, or minimizing the alternative... I dunno, make more people read some Peter Singer? Again, box of chocolates, with some of the chocolates being filled with dirt.