If that fails, what I’ve seen others say works is if says he’s an alpha male say back “I’m not into that furry stuff, but that’s really cool your so open with your sexuality like that, and accepting of others’ sexualities like recognizing the beta males”

I doubt that actually works to get people off that mindset. It's just a funny twitter joke people have latched onto. Other than that 100% agreed. If he's fallen into this manosphere shit things probably aren't going well for him socially and he probably needs help to get out of it. When I was young I certainly did and was fortunate enough to get into a much better environment after I got out of high school that corrected my mindset (for the most part, there's always a need for self-reflection). While deserved, ridiculing him for these beliefs won't get anywhere other than to make him feel more isolated.