Truth?
There's really no difference between Holocaust denial and "holodomor" denial except that one of those things is correct and the other isn't. Holocaust denial isn't bad because you're denying a genocide, it's bad because you're denying a genocide that happened and for which there is overwhelming evidence.
If it were wrong to deny any genocide claim, then the perfect attack to make against any political opponent would be an accusation of genocide. You could accuse literally anyone of genocide at any time and if they deny it suddenly they're the same as a Holocaust denier. Obviously that's absurd and invalid.