Troublesome Necromancers

I'm kind of a new player and I've been playing D&D 3.5 on Roll20. In one of my campaigns, there is a necromancer and I found out in my new campaign that started yesterday, there's another necromancer. It seems kind of unusual that DMs allow PCs to take that kind of class-- why would any other character hang out with a necromancer? In both, I had to change my alignment from LN and NG to true neutral so it made sense for the two characters to be in a party together. It doesn't seem to be like a good style to play in if the characters' goals conflict and you have to justify why such-and-such doesn't outright try to kill the other guy.

So my question is whether my playing style conflicts and I should just try to find new games or what?

It does sound like you should try to find a group that fits your style. Now you know to ask the DM if evil and Necromaner characters are going to be allowed and avoid those.

Yeah, necromancers aren't "troublesome" so much as they are markers of a less-heroic sort of group. (I can see a number of Lawful Neutral characters being just fine with necromancers, for instance. Tywin Lannister would be A-OK with them, for instance, so long as none of those zombies were blondes.)

So yeah, do find another group, but ask if this is going to be heroic adventure or something a bit grittier. The grit's not what you're looking for, so everyone wins by the DM being clear about that up-front.