Probably the same thing as doing anything else objectionable: It depends on how offensive the Good NPCs find it. There are good necromancers and terribly pragmatic people of all alignments who'd let it pass. Others might not. Heck, there will even be evil characters who will violently object.
That is an issue. Everyone needs to be on the same page, and the players need to trust each other. All I can say is talk it over with the other people in the campaign, openly discuss everyone's boundries boundaries, limits and confort zones.
This is true if and only if part of the working together includes possible redefinition of the terms "Good" and "Evil", or in some cases redefine the personalities of existing characters, or in one case (Paladins) redefining the rules of the game.
Are you really suggesting that there are times when groups shouldn't try and work together to make the game enjoyable for everyone? That can't be what your saying, because it wouldn't make any sense.
What's wrong with the players and DM conspiring to create a context in which good and evil characters can work together? And how does that equate to 'redefining Good and Evil'? Even if it did, so what, if we're all having a good time?
In every campaign I've played in, people have had to redefine their characters to some extent in order to accomodate the other players. I've always felt that was a skill to cultivate when playing RPG's, since so much of the game involves negotiations and compromise, in the both the in-game and metagame sense.
As for Paladins... well, yeah, they're screwed.
This rather gets into the realm of, "Sure, you can fit a square peg into a round hole - if you are willing to employ a chisel."
Not to wax all "Matrix-y", but... there is no peg, there is no hole, and there sure as hell isn't any chisel. Finding reasons for a group to work together is only as hard as you make. Consider how fraught with improbability the iconic party is; knight, priest, heathen wizard, and guy who steals things. And the iconic meet-up scenario; "Uh... you all meet in a tavern". No-one complains too loudly about the logical loopholes required to make that work, so why is it so different when it comes to rationalizing why differently-aligned characters can adventure together?
Stressing what can be done rather glosses over the question of what should be done.
A lawful evil villain methodically takes what he wants within the limits of his code of conduct without regard for whom it hurts. He cares about tradition, loyalty, and order but not about freedom, dignity, or life. He plays by the rules but without mercy or compassion. He is comfortable in a hierarchy and would like to rule, but is willing to serve. He condemns others not according to their actions but according to race, religion, homeland, or social rank. He is loath to break laws or promises.
This reluctance comes partly from his nature and partly because he depends on order to protect himself from those who oppose him on moral grounds. Some lawful evil villains have particular taboos, such as not killing in cold blood (but having underlings do it) or not letting children come to harm (if it can be helped). They imagine that these compunctions put them above unprincipled villains.
As my girlfriend pointed out after her first job in an office, many large Corporations would qualify as Lawful Evil. They do whatever they can within the laws to make as much money as possible, regardless of whether they mistreat the environment, the populace, or their own employees.
Lawful Evil does exist in the real world...and it co-exists with everybody else without too many problems.
Players took alignments for their characters, and in doing so sent the following messages to their DM:
Lawful Good: 'I'll be pushy and shove others around, but not so much the DM stops me. I'm experienced socially, so I'll get my way in things.'
Neutral Good: 'I'll behave myself, so I can stay in the group.'
Chaotic Good: 'I'll try to get away with as much as possible, without alienating everyone.'
Lawful Neutral: 'I'm here to fit in. I'm a team player.'
Neutral: 'I want to play, but am not sure how I fit in.'
Chaotic Neutral: 'I will run riot through this scenario. What, there are other players at the table too?'
Lawful Evil: 'I know how to mess over the other players, and will. But I'm clever enough to get away with it.'
Neutral Evil: 'I'm here to mess everyone over. This is about fun? Yes indeed: my fun.'
Chaotic Evil: 'I'm here to mess everyone over. By the way, rules do not apply to me.'
It shouldn't have been that way, but that was the way it was.
Here's MY idea of the message that ought to have been sent to the DM:
Lawful Good: 'I want to have fun, I want all of you to have fun, and I want the DM to have fun. My character will act like this (description follows) if the DM deems this will fit within his scenario and everyone else is reasonably comfortable with it.'
Neutral Good: (as above)
Chaotic Good: (as above)
Lawful Neutral: (as above)
Neutral: (as above)
Chaotic Neutral: (as above)
Lawful Evil: (as above)
Neutral Evil: (as above)
Chaotic Evil: (as above)
Mature players appreciate party infighting ruins the game and wastes valuable real-world time.
Immature players ... are immature players ...