At the end of the day, all you can do is the best that you can do (& clearly have)... & they're going to choose what it is that they choose... So, there's not a lot you can do to change that. Ultimately, you can influence them and persuade them, help them to try to see the light, or the error in their ways (only so much). For it is up to them to then decide that they wish to follow through on such things and then (to) implement them. So while it feels as if the burden lies with you. It does not. They are responsible for their own behavior(s). And sometimes, there's not a lot that you can tangibly, or credibly do, to make a difference - again, in the end.
Sorry for sounding so morose. But that is my opinion, and my view - or take - from having been on both sides of it. . . You're right to not let it fester, or it will continue to eat away at you (when there's really nothing you can do) and eventually, or up until it consumes you. And that there then is never a fun place to be. Take it from me. You'll go insane. Or feel as though you have (driven yourself there). . . So you have got to protect yourself, choose wisely, set up boundaries and understand where they lie, and simply "how much is too much?" Or when you think you have strayed too far~
Now wait a second? Why are you saying it's shameful, again? And what exactly, do you mean by it? That you somehow are? Because I hope you're not (feeling that way & implying something else entirely). I just can't read & interpret (isn't that comprehend? ) any-thing, right now. Please forgive me. I know not what I do... : )