Where they justified in turning them to stone? Yes. Each one of them was still a threat and they had previously tried to deal with before. I think this was directly done do to how so many fans hated how everypony was getting redeemed left and right and I think it's 100% fitting for Tirek and 80% fitting for Crissy (because a redeemed Chrissy would certainly be interesting and have a lot to work with with how much hatred she holds and how long she has been a foe). Cozy Glow is still a bit of a moral question but I think that goes back to season 8 when they locked her up in tartarus. They could have had her reject friendship and redemption better in season 8 or a another momenet in season 9. We never really knew how she became evil and her full backstory and if these had been explored better we have better perspective and it would have felt more satisfying rather than the big question marks left over our heads with her. After all, the incomplete exploration of the character and her ideology have caused some even so far as to view her as a martyr to a subverted truth on Equestria friendship is magic, but magic is power They were fully justified in taking out a rough alicorn in that moment though.