As someone who has worked with teenage boys, most of whom actually liked and/or respected me, the best tool I had for shutting down edgelord bullshit was a flat stare and “you’re better than that”. Simultaneously conveying “I am disappointed”, “I have expectations of you”, “you have otherwise met them”, “that sort of behavior is unacceptable”, and “you are better than the people who engage in that sort of behavior, but only so long as you don’t join them.” is an incredibly powerful tool with kids who care about what you think. The worst I ever had to escalate to was ‘disappointed headshake and “I thought you were better than that”.’ I’ve never had to repeat the sentiments or escalate after deploying that one. Actually made one of them cry once with just that. He felt that bad about letting me down, and we had a solid talk after. With guys my age, “I guess you’re not the kind of man I thought you were.” has proven effective.