The difference between then & now is the knee-jerk coded-language condemnation of "head cases" that the NBA Cares so desperately to avoid.
That may or may not be a difference, but as it applies to the reaction and punishment, Maxwell-sitch vs Artest/Pacers-Pistons Brawl, I don't think it is the difference. We know that, from a marketing perspective, the NBA of 1980 is nothing like it is now. It's ALL about image, and - as we saw when Horry's cheap-shot on Nash led to leaving-the-bench playoff suspensions for Amare and Boris - Stern runs a tight (maybe, at times, irrationally inflexible) ship. Combine that with the facts that Maxwell's incident - according to the video - did not escalate into anything close to the degree of the Pistons/Pacers brawl (Kevin Loughery says "could've got real nasty out there"), and was not an ESPN/FOX Sports/CNN/Internet staple for days (IOW, media then vs media now), well you get the idea.
Was Artest's suspension longer because of his past and his rep? Probably. In fact I seem to recall that Stern said he took that into consideration. However, I don't think there's much doubt that if it wasn't Artest but was instead some average NBA player, w/o a "problem background," there still would've been a bunch of suspensions and crackdown.
There are plenty of differences between the two incidents, but so much else is different between now and then.