“what they consider” being the important part here. People are zealously against what they consider the dilution of the “white gene pool”. Does that make them right? People are zealously against what they consider robbery by the state of their hard earned money. Should we condone it because they are zealous?

Yes, zealousness isn’t bad in and of itself, nothing is. Everything is a matter of perspective. Maybe murder of humans could be considered a valiant, virtuous, and veritably honorable thing to do if one thought it could fend of the mass extinction event we are in. Rape could be justified by rapists as a necessary action to spread their seed.

Vegans aren’t the only people with justifications for what they do and what they consider right.