@stefano wow, this post was perfect to fill a wiktionary entry for the word « assholes ». Those “great managers” doing harm so easily by just being dicks. Sorry this reply should not contain obscene words, but as it makes me think about own past experiences, I am probably overreacting… for the remaining of the company, and the team you are collaborating with, it will be a relief. You saved their day(s) by pushing things a little. It escalated, stack overflow.
Your position, being prudent, for a new collaboration, is the best one. You secure your work, the company will remember to secure the relationship step by step. Because confidence being broken can’t be resurrected in a click… there is no such thing as “business relation snapshot” to be restored. Green field, built brick by brick again.