For example:
Carnist: "Hey, you want a slice of this pepperoni, triple cheese pizza?"
Vegan: "Sorry, no thank you, I'm vegan."
Carnist: "Oh, wow! Nice! I respect that! Yeah, I would go vegan, but I just would struggle with protein, B12, and iron if I did! Like, I tried being vegan for a week and got so sick! I still eat plant-based alternatives every now and then, though! And I totally get where you're coming from with your ethics! Yeah, the way they treat animals on those factory farms is crazy, bro! I hope those cruel practices can be abolished one day. Complete solidarity with you and the animals, dude! ✊ In the meantime, I absolutely try my best to get my meat, dairy, and eggs from local, free-range, humane, and organic farms!"
Vegan: "Okay?"
Like, seriously, just saying "Oh, okay." and moving on with your life would be preferable over this shit.
No apologism.
I'm not going to condone babysteps. If someone tells me that they're going to "reduce" their animal product consumption, I, at my best mood, will be like, "Okay, sure!" but I absolutely will not cheer them on as if they're doing something spectacular.
You always should convey an abolitionist, vegan message, and if what you get out of it is them saying that they'll "reduce," you obviously can't "force" them to go vegan overnight, and I understand that such a change can be initially hard to grasp for many people, but it's important to remain principled in conveying the vegan message at all times.
If I condone babysteps as a "good" thing, I'd be inadvertently giving off the notion that "some animal slavery is okay." You can acknowledge the flaws of such an approach while not being "rude" or "disrespectful." Being unapologetic and kind are not mutually exclusive.