Morgase loves her children irrespective of their faults, like any mother, the Whitecloaks accept anyone who demonstrates he shares the zealotry they value above all, Gawyns attitude is more blind hero worship than seething envy and Mat's not exactly the type to consider a model of proper behavior a positive thing. In the end, however, what sunk Galad for me (apart from the fact that I've never encountered a version of Galahad I wouldn't cheerfully beat to death) was joining the Whitecloaks. That whole organization is an institutional embodiment of doing the wrong thing for the right reason, so even without the foreshadowing it wouldn't have been suprising that Galad wound up there. Even if it's not integral to Mantelars manifesto, hunting Aes Sedai as "witches" IS integral to the Whitecloaks now, to the point that their own version of Torquemada overlooks an assassination and coup because he resents his superior withholding Morgase from the rightful torture and execution anyone who's so much as seen the Tower deserves. Galad walked blithely, eagerly and knowingly into that den of madness because the Whitecloaks brand of unreasonable zealotry resonates with him; the conflicts that created between his personal and doctrinal honor are no more than the poetic justice he deserves. He owes Elayne and Nynaeve a favor for never revealing to his cohorts that they can channel, or the immediate demands for their arrest (at best) would've forced him to choose between harming his sister or betraying his oaths to the Whitecloaks. It's a foul organization where integrity and virtue are the exception to the rule of fanatic viciousness rationalized by dogma, and Galad merging so seamlessly into it was all I needed to confirm Elaynes assessment of him.

The Whitecloaks manifestly and routinely engage in all of those things, something Galad knows better than any reader. When he gave them his allegiance, he was fully aware he was giving it to all those things as well. It's pretty clear Jordan intends him to be a reforming influence on the Whitecloaks, and he can write the narrative to make that as successful as he likes, but, realistically, Galad has always had too many of the same traits that encourage zealotry, fanaticism and brutality in the Whitecloaks, so the prospect of him moderating and restraining those impulses isn't very plausible. Galad is too concerned about the letter of the law at the expense of its spirit, which is how a Whitecloak organization founded on the noblest aspirations degenerated into the vicious reign of terror it has since become. "The Children have authority wherever the Light is, witch, and where the Light is not, we bring it". Let's not forget that Galad still counts the man who spoke those words among his cadre; while Gawyn collected the Younglings, Galad collected men like Dain. He may like to delude himself that Eamon Valda represented a minority of Whitecloaks, but their history as presented in the series strongly argues otherwise. At best his membership in their order is remarkably poor judgement in an otherwise very intelligent and experienced character; at worst it's an acknowledgement that even their most brutally draconian practices are justified so long as the victim is duly found deserving. I guess what I'm saying boils down to "lie down with dogs, wake up with fleas"; Galad joining the Whitecloaks knowing their extensive institutional record of legalistic cruelty demonstrates a tacit approval unsurprising in light of his own legalism.