I sent a 'friendly' because I agree with the point you made in this post, but I have to say I don't agree that the statement was offensive "because it equated those who believe in a spherical earth with abortionists." I would say that the statement was taken to be offensive because some equated the two, though the statement itself did not do so. But somehow I think you understand this and I'm not actually correcting you on it. And I'm certainly not stirring the pot. This makes two threads I've started in all sincerity that have already been filled with irrelevant discussion.
As far as threads going awry, I am as guilty as anyone concerning this for a number of reasons. But it is difficult to consider a particular topic without ancillary topics arising as well.