Answer: It might help to recognize that your letter is a snarkless version of the bottle-bottle-explode tactic the boyfriend uses.
When he disparages someone or something, he hands you an opportunity to say, "I'm sorry to hear that; I'm having a great time." Or, "Why'd you come, then?" Or just, "(Shrug). Your loss." Right? Your words, of course - but as long as you're dukes-down and not fighting snark with snark, these are opportunities to express your feelings not just honestly, but also to the source.
Your calling out the poor sportsmanship might move your friend to start the conversation anyway, and that's OK. Even if he's defensive, keep "He's a soul-sucking, spiteful, passive-aggressive joy vampire" between us, and stick to "I think it's fair for me to respond to his comments" or "How do you feel when he says (latest example here)?"
Your behavior change, though, in limit-setting versus avoidance and excuses, might on its own spur a behavior change in the boyfriend, your friend or both. And regardless, you'll have done something. Isn't that what you want?
Q: My sister was married 41 years and her cheating husband died of lung cancer four months ago. She stayed and took good care of him till the end.
Three months after he died, his high school best friend (her first love) came to see her, and now they are engaged. She wants to get married yesterday.
I've been asking her to wait, slow down, etc. What can I say to persuade her to give it some time?
A: It's easy to understand your concern, but it's hard to summon motivation to find ways to interfere with a grown woman who is living her life as she sees fit.
It's also easy to see how the promise of a little joy is more persuasive to her than your forecast of doom.
While your impulse to warn is natural, you'll be more credible to her if you acknowledge her view.
After you've shown that you understand, you'll make more sense to her when you say, "This sure does look wonderful, and in a year or so you'll know whether it is."
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