There's no reason why even vehement disagreement can't be carried out politely. I've never seen a reason for anyone to be mean-spirited, no matter how much disagreement, on simple particulars or fundamental principles, there might be. When people disagree with me, we can continue the discussion, at least sometimes (occasionally, we must agree to disagree). When they venture into insult, however, they've told me that polite argument is no longer of interest to them and I stop participating. I consider a "safe space" one in which the participants generally agree to this.

That said, there's also no reason to feel hurt if someone meticulously dismantles an argument, as opposed to ripping it to shreds. :-)