If you're genuinely getting PMs which are personal attacks on you and full of vitriol, as you say, then it seems a perfectly reasonable question to ask. And if they are as you say they are, perhaps a word with a Mod may be in order - it's difficult to advise without knowing substance and context.

I don't believe that PMs of that nature should ever be sent to another 'Catter. We may squabble, argue like cat and dog, shout at each other and be generally sarcy and picky on the Forum, but there's no need to take such stuff as far as a personal attack. There's no need to get nasty in private, no matter how serious or entrenched the debate. I've let rip, now and then, in the past, but I resist the temptation now.

But what do I know...