but she's still be alive and he wouldn't be heartbroken

It's just depending on the person. Maybe he just rather has it and then lose it rather than not having it at all. This is still something that is beyond RR's control though since it's not something they can't be blamed for. What they can be blamed for is giving synth crappy childhood that lead to many synths leading crappy life like becoming raiders. What pissed Danse off the most about being a synth wasn't that he was a synth, it's that they don't even bother to give him a happy childhood with family or sibling. He was always alone and has to fend for himself growing up without ever feeling loved or wanted.

It's exactly within their control; they're the one wiping their memories in the first place. I know they do it for safety reasons or whatever, but it undoubtedly has ripple effects that aren't always beneficial, both directly as you suggest and indirectly like with Deacon's wife. I just think that Deacon of all people should be able to see that himself, but I guess he's too caught up with his own past and wants to 'reverse' what he did in his youth as well as wanting to 'avenge his wife'. I'd consider it just as realistic for him to be angry at the RR, but I'm okay with the path Beth chose for him, too.