My problem with "animate dead is evil" is that they should state why it's evil; and specifically, whether they're talking about "evil" as a cosmic force or "evil" as immorality.
If they mean evil as cosmic force, then there's nothing morally wrong with animate dead, but the spell carries a taint of corruption and casting it increases your Lifetime Evil Exposure. Cast it a lot, and you will start setting off paladins' evil-dar (if that exists in 5E), being affected by anti-evil spells, et cetera. When you die, your soul will end up in the lower planes, even if you created and used your undead army for good purposes. Life isn't fair sometimes. Them's the breaks.
If they mean immorality, then there must be something that is actually morally wrong with creating zombies, and they need to specify what that is. Disrespecting the dead is pretty weak; even setting aside that disrespecting the dead is a routine part of adventuring, it's weird to call out disrespect for the dead when you can disrespect the living all day long. Perhaps undead are a walking blight, draining life from the world and spreading despair by their very existence. Perhaps undead are inherently malevolent (so skeletons and zombies are evil-aligned, and will rampage and kill unless specifically restrained from doing so). Perhaps the soul of the dead person is tormented as long as its body remains undead. Perhaps each undead created strengthens Orcus and increases his influence in the mortal world. Any of these, all of them, something else: Pick one.
I agree with the sentiment that making undead is the sort of thing that should move a PC toward the dark side, but just saying that certain spells are evil is not enough. Either go into detail or don't say it at all.