He has every right to be pissed. I don't agree with giving any significant input on the hiring of a GM to a player, but you can't say you will include him and then blindside him. That's apparently what the Raptors did to Vince Carter and it led to a significant fall-out. At least work to explain why you hired that guy before you publicly announce it. But, it seems like as far as he knew they had a list of 5 and were working it down, and then he found out they hired someone not on the short-list who is heavily linked to Easterby who he doesn't like or trust (due to apparently leaking that Watson and Hopkins didn't get along, which wasn't true).
But, Easterby seems like a charlatan who has people in his web through his mix of religion and personal coaching web and has maneuvered himself into a position of great power within the organization. It's almost impossible to come to the conclusion that the hiring of Caserio was independent of Easterby. Now, the Texans have to follow through with either hiring a coach that the QB wants but the front office doesn't or further alienate Watson. Either option is likely to end terribly, as the key to organizational success in the NFL is alignment through all levels. In my eyes, Bieniemy would be stupid to take the Texans job at this point, it's a poisoned chalice. The only option that seems to actually work is bring in someone in the Easterby/Caserio network such as Daboll or McDaniels, and get a king's ransom for Watson and hopefully leave the draft with one of Lawrence, Fields, or Wilson, and a ton of draft capital to make up for the stupid Laremy Tunsil trade.