Despite your edit, you still have an out-of-character problem more than in-character one
Basically, even if your character’s actions were appropriate and acceptable, and your allies’ actions were appropriate and acceptable, there is still an out-of-character problem because you are still expected to play together as a group.
Be sure everyone is on the same page
But first make sure everyone is on the same page. The bard’s player may be fine, but it is still unclear whether or not the others are. The first step is determining how they feel about things out-of-character. If they feel it was a dick move, then there’s still an out-of-character problem. Personally, I’d argue that it’s not their place to hold the bard player’s grudge if he doesn’t mind the result, but they may be thinking about their own characters – you may have to think about reasons why your character would treat their characters differently from the bard, since they may be off-limits.
Even though you say these things are OK at the table, I think it is a good idea to discuss them explicitly:
Is player-vs-player violence acceptable at this table?
Are players comfortable with you raising their characters after death (regardless of how they got there)?
Do the other players enjoy your character’s antagonism? Does that make the roleplay interesting for them, or is it just annoying?
Be prepared to get answers you don’t want. You seem to have taken some liberties with your character and how he affects the other players, and they do not sound appreciative.
And then figure out how the party stays together
And then you need to discuss how the group is going to stay together. There are basically four options:
The group comes to an agreement about how to make things work.
Your necromancer leaves.
Your necromancer dies.
Your necromancer kills everyone else, too. Depending on the relevant builds and resources, this will range from “difficult” to “impossible.”
Since three out of four of these end in the dissolution of the party, if you intend to continue playing this character, you want to focus on option numero uno: make this work.
A great starting point (and credit to @BESW for reminding me of it) is Rich Burlew’s Making the Tough Decisions, particularly the section starting with Decide to React Differently. Ultimately, all players are responsible for how their characters act. “That isn’t what my character would do” is not a defense of anything; you decide what your character would or wouldn’t do. It’s quite possible for even an Evil Necromancer to begrudgingly respect a comrade enough not to animate his corpse, if only because the comrade wouldn’t have wanted that to be done. Besides, in the case of a bard, it’s not like the zombie’s going to retain his singing voice.
Basically, properly motivated, you can think about how your character would rationalize any given decision. You shouldn’t do it too much – that dilutes the character – but no one behaves 100% consistently all the time. And when the alternative is breaking up the party and ending the game, well, the priorities here should be clear.
This goes for your teammates as well as yourself. Ultimately, they are partied with an Evil Necromancer; loyal sentimentality and respect for the dead are not exactly reasonable expectations here. I suggest everyone read Rich’s advice, and I suggest a discussion of exactly what the table wants.
Finally, after the discussion is over, do not be afraid to ret-con the situation if necessary, or if not, suggest ret-conning the other characters’ responses if they would not have known what happened. Then again, they may be entirely justified in objecting to the animation of a comrade, even one who died “naturally” – after all, you’re eliminating the chances of resurrection.
Ultimately, if you continue the game as-is, you’re almost certainly dead, or at least out of the game as your necromancer leaves the party since it’s pretty obviously not safe for him. You have to figure out the out-of-character stuff in order to survive. Dread Necromancers have a fair few potent defenses, but ultimately not enough to continue to attempt to cooperate with people looking to kill you.
That said, it may help you come to an out-of-character agreement on how to “spin” the in-character agreement so the party continues if you have some mechanical back-up. Dread Necromancers are heavily focused on Charisma: yours should not be bad by any means. Come up with arguments that your fellow players agree would help their characters accept the situation (or the altered situation, if necessary). Reference your sizeable Charisma as justification that your character could make those arguments.