fallout2 Frank Horrigan Dialogue HELP

[chainerror25]

Does anyone know how to trigger frank horrigans dialogue where he says " Dumping the F.E.V. toxin into our air doesn't make you a hero. You're just another mutant that needs to be put down"

and also this one

"You mutant scum! Just like you to try a trick like that. It won't help you though, nothing will... now "

I've tried activating the toxins in the air but he doesn't acknowledge that once I speak to him at the end

and I have no idea how to activate the "you mutant scum!" dialogue, I would really appreciate any help