To be fair, the argument against calling Pluto a planet was really political more than scientific--it's hard to argue that there's some nonarbitrary scientific justification for removing Pluto's planet status.
I'm sure those on the other side of the debate would argue that it's just as political and arbitrary to claim that it *is* a planet, beyond pure inertia (i.e. because it had always been called a "planet" until then).
Two wrongs don't make a right
Anyway, they were Pluto-haters, or haters of the idea of smaller planets messing up their tidy worldview.
Now I think you're trying too hard to rationalise the "haters" label. As I said, you don't have to agree with their opinion, nor the way they went about getting the result they wanted.
But that doesn't change the fact that dismissing their opinions and actions purely as "haters" was quite silly.
If the argument had started to become too personal, then this sort of concerted attempt to justify that way of thinking simply makes it worse. As you said, two wrongs don't make a right.