Kevin can be very opinionated but he is simply not a fool. I also disagree with him on this one and I'd say, from my experience, that his post reflects ignorance of the varieties of Tai Chi practice that can be found. Neverheless, I found his post interesting and thought provoking.
On the subject of gentle martial arts: a friend of mine who is a sandan in Tae Kwon Do took up Aikido in part because he got tired of feeling confined to violence when faced with threatening situations. I think there is a question of where we start saying the martial art is being used. Aikido, for me, has always had a focus on how my bearing and attitude can gently discourage conflict. This is different from seeming deadly or intiimidating, which I would say are non-gentle means of dissuasion. I would imagine that the more gentle the lead up to physical violence is, the easier it is to be gentle once things do get physical.