There is no excuse for being a rude jerk at the game table.
Lots of good advice in this thread - I wish I knew how to recommend it for a Game Table Self-Help sticky or archive.
Back on topic. IMO, the ideal setup with old school gamers and new school gamers is this (in very general terms): The old schoolers kick back and watch the new schoolers go crazy and have fun. The old schoolers use the tried-and-true tricks of the trade to help speed the game along, so that everyone can get to the bits that they personally enjoy most. The old schoolers offer *advice*, OCCASIONALLY. But with the understanding that it's not their character.
The new schoolers go have fun, show the old schoolers the new stuff to try that hasn't been tried before, point out rules that help the game flow. New schoolers try out the oddball classes, add some randomness and "new" fun. But do it with the understanding that some other players at the table have been there/done that, or have a different approach that takes time and patience. I love it when new schoolers go against the old schoolers' advice, emerge victorious, and everyone laughs about it for weeks afterwards.
Most of all, the players are working together, and with the DM, to help make the game session fun.
Notice something: Both sides are being courteous. Both sides are working towards *everyone* having fun. No one is trying to cram their personal play style down anyone's throat. Disagreements are handled quickly, with respect, and kept to rules issues. Personal issues get handled away from the game table.
It sounds like you may have one problem player who is riling up another player, and creating an unholy pain of an Us vs. Them situation. This ruins everyone's fun.
Talk to your players (which you are already doing). Find out what's bothering them. Get them talking to each other. If they can't work it out, then you will have to - and that will likely mean one or more people leaving your game. It sounds like you are already heading the right way.
Do it with dignity, do it with grace, do it with courtesy and respect. But do it quickly.