At a risk of repeating myself, a good rule is, as in soccer, "go for the ball not the player" .
I like a good disagreement myself. When we have reunions of our extended family there is lots of debate, with political views ranging from Tory to Trotsky.
I was also educated in a tradition where debate is seen as a good thing. My DH is more of a pure scientist (physics, maths etc) and did not experience this sort of thing in university. Also his family never debate and rarely disagree. So it does depend on your background how comfortable you are with people disagreeing.
I think it behoves us to be careful about how we express disagreement and likewise, to take a deep breath and ask ourselves "Am i being got at, or just disagreed with".
I had to pull myself up the other day when someone posted some views that I thought were somewhere out on the wilder fringes of reason.