I wouldn’t be offended. “Papist” is an insult from non-Catholics.
I don’t see why ‘follower of Martin Luther’ is an insult to Lutherans. You’ll have to enlighten me.
Lutherans identify with “Followers of Jesus Christ”. The point being is that Luther was not/is not infallible. We don't claim that.
And considering that this site has some who constantly claim that
1. Lutherans are not “real” Christians.
2. Lutherans worship Luther.
I can see some getting touchy about it. In fact I expect a few to arrive shortly, who will start saying that Lutherans (and all non Roman Catholics) are indeed damned.
In other words, welcome to the religion forum. Poo gets thrown here.
The term "Lutheran" originated as a perjorative which was eventually accepted by members of the faith because it was reasonably descriptive and, besides, it's much easier to pronounce than Melanchthonians.
We don’t “follow” Martin Luther. We follow Christ. Luther is in many ways inspirational but some of his teachings we reject utterly.