Namechanged as this is sensitive and could be outing.
Had a party on the weekend for DC birthday, family around, lovely time had by all. My parents stayed on a bit.
DF mentioned that he'd seen something for a car I have off the road at the moment, a lot cheaper than I would have expected. DH commented that that may be the only option, but we've bought a part and waiting for someone to quote for the work, and there are various avenues we could explore. DF shot down everything DH or I said with "yes, until it stops working". DH said that while he's probably right, we'd like to try out what we've thought of first, as we won't know unless we try. No need to worry, it's our car, we'll sort it.
DF then stormed out of the kitchen swearing saying he couldn't listen to this anymore and wouldn't sit there and argue with DH 
This is not the first instance of total overreaction on his part while in conversation with DH. It really upsets me and yesterday it ruined the lovely afternoon we'd had. Very tempted to just go NC, but I'm not sure how it would work if he lives with my mum and I still have a good relationship with her.
Anyone ever done this successfully?