Learning a language is an investment. People defend their investment strategies lest they be considered a fool. Attacking alternatives is a form of defense. I fear it's as simple as that.
The original question was -- why do some communities seem to be more oriented towards language wars than others?
Can't speak for all of them, but if a language has "there's more than one way to do it" as its main motto, I guess the people from the ecosystem are less likely to attack other languages.