I don't agree ... votes should be given for any reason a reader wants. Sometimes the actual post is so stupid and off-topic that it doesn't deserve a response ... and the rating system is there in the first place to distinguish between the good posts and the bad ones.
Granted ... this particular comment was pretty much on topic, and contains a very popular point-of-view in many circles ... so personally I haven't down-voted "theotherside", preferring to give him a reply instead.