Tips for tongue biting..

So.. in laws..

We all have horror stories about the in laws I'm aware. But my SO recently came back from a military posting. And when we were preparing for his return I got to spend a lot of time with his family and father in particular. This man who has openly put down and disparaged his sons choice to join the military in the first place is now buying shirts and stickers with it on there to show off on Facebook. Everything is about how many likes he got. How many comments. Not about his son. He is the most self centered person I have ever met. Has no issue telling you wow you're a bad driver. Or how did you make all A's? You're dumb? Or your church does it wrong.

Complains about everything. Everything. And frankly after being insulted for a week straight and just disgusted by how he treats his family and how he has acted and thought only of himself when it this should have been about his son.. idk how to keep quiet. My SO knows all too well how his father is but I still don't want him to know all of the childish and selfish things his father did this week. But it gets so hard to just ignore.

How does everyone else deal with their unpleasant at best, abusive at worst in laws?