Sadly enough, compared to the other methods, the Ashaman's method of poisoning the mad really is the most merciful. I mean, let's take a look at the others.
Aes Sedai: Gentling and then being tossed out to fend for yourself. Not only are you suicidally depressed, but chances are everyone's...
My main issue, like what Eluiel said, was the Aes Sedai's behavior towards gentled/stilled men/women. They pretty much treated them like they were plague victims. As far as I know, they only tried to keep one alive (Logain). They simply gentled Thom's nephew and left him to rot.
This also...