I’m sorry, I am confused—English is a second language, you see—is it that ‘mass murderer’ is a gentler term than ‘terrorist?’ It does not strike me so, but I could be wrong?
As for my own motives for insisting on correct terminology, apart from inherent pedantry of it which I confess is a factor, I am motivated by the horrible excesses perpetrated in the name of stopping terrorism. I would not feed that particular beast without good cause.