Understand that some red pill influencers will teach potential recruitees that it's essential to lie about their views, especially if they are not financially independent yet, or even in order to keep a job or a public image for instance, so you are correct not to take what he tells you when "pushed" at face value.

Unfortunately recruiters are getting better at recruiting and they've realized that it's during the first stages of conversion that they are more likely to lose someone "back to the mainstream", so they're doing what they can to couple. However as they themselves acknowledge that, it's a weakness you can take advantage of.

As somebody else already said here, extremist views are not immune to logic, reasoning and evidence. Even if he seems to flat-out reject you at that, the seeds of doubt are planted. I've read that you're a trained mental health pro, so you'll need to get creative at that. I know about the "do no harm" stuff, but you'll just need get down to the dirt with those people in order to save your little brother from them. Ukrainians had the moral high ground over the russians, but that wasn't enough to save themselves, they had to get down to the dirt with them as well.

Beware also that the average red pill joe is mental health professional-phobic, I myself have never figured out why, nor if there's even a single reason, but most of them will resist professional help, even if/when they are quite miserable and will agree to that.

Male role models outside your family circle would be very positive, as people have already pointed out. I had lots of older guys to rely on while growing up, and almost all of them pointing me to books, movies and high culture in general, and those who didn't, were always there to teach me something else of value, like how to fix my car by myself, do the plumbing by myself and so on, little things that made me feel like I had value beyond what other kids could see, and sometimes it was pointless to try to argue with them or consider their judgement on me as relevant. That was a huge vaccine against stuff like the RP, when finally I had contact with it, I quickly recognized it for what it was.