I see what you mean, but I think I view the comment slightly different than you do.
On one hand there's nothing wrong with enjoying singing covers with a band if that's your joy. On the other hand I think Rebecca had an idea she was almost picking up where she left off years ago and still had an idea she was on her way and growing her singing career into a major career. I don't think that was true of where she was headed as a very young woman and I don't think it's true it was anywhere close to her grasp these years later. I don't have a problem with Jack verbalizing that truth to her in a way to bring her back to reality.
Like I said, I think you receive the message differently than I do. It's all good, I tend to like unvarnished truth more often than not and people who don't know me can think it's kind of harsh, so I'd expect others to view it differently than I might. My husband and I rarely argue and even have a strange shorthand between us in communicating when we disagree, so I can't even imagine the idea of, I think you should go stay with Miguel for a while so we can take a breath. I think that's why I can't understand some of the comments about the episode being boring or not leaving us with much drama. That kind of thing would be absolutely seismic in my world.
I wouldn't say we fight "dirty" by any means. But I think we can level with each other at depths that might bother others. Not mean or toxic, not even loud or raised voices, just really level with each other with an understanding that no matter what we are united. Kind of hard to discuss in writing with strangers without coming off like Princess Perfect with the perfect marriage in the perfect life, etc. We're very, very different people who have our struggles and we disagree about lots of things. Surprisingly it works with relative tranquility somehow.