Sadly when people post those messages it's purely for a ranting nature. They're not open for debate, it's a topic that will have no discussion and automatically because we like a character we automatically agree with everything they do or are believed to have done. Does every Anders fan condone terrorism/bombing civilian housings? No. Does every Sten fan agree with the core tenets of the Qun? Of course not. That's not to say that they are totally against it, but they might dislike his philosophical thought process, but not the teachings in and of themselves.
I honestly have little to no opinion on Alain, why? Because I have very little interaction with him. Alain to me was a scared but faithful guy. I sympathized with him, because honestly I dunno if I could handle life outside the circle if I was him. I hate what happens to him, I ABHORE it, but I'm not gonna blame Cullen, for something he might not even be aware of, just like I don't blame the parents or spouse of a serial killer, Sometimes these people are attached at the hip, but they still don't recognize what's happening.
There aren't any real clear cut signs. I'd like to believe Cullen had no idea what was happening or conversely that he was trying to stop it, but if he was aware and did nothing/let it slide then he better have a good damn reason otherwise I might "disown" him.
Until then I'll follow DG's quote that he's one of the good templars and if I feel a compulsion I'll like Alain as well, but currently he just doesn't...compel me like some other characters.