I work with a lot of guys into (or adjacent to) the "I'm deeply insecure about myself" part of the manosphere. Testosterone supplements, sildenafil, meat heavy diets, etc.

I usually ignore it, but sometimes they start pushing that stuff or talking down to me about it. The easiest way to shut it down is playing off their insecurities.

"I'm already a man, I don't need gender affirming care." Followed by asking them how their transition into a man is going -- most of them are highly transphobic.

"Why? Mine [dick] works fine, but I'm glad you found something that helps."

"I don't do fad diets."