Here are two generalisations (if you haven't already, read previous entry first):
Left-wing folk object to TCS because they view all sorts of things as coercive, and see parental coercion as miniscule in comparison, and a defense of children. For example, some lady got the word "gun" removed from her daughter's spelling test. One can imagine the reaction if her daughter wanted to get a gun, and write gun a bunch, and draw gun pictures. The justification? In essence "guns are coercive/bad". Another common one is "TVs are coercive/bad" and therefore must be kept from children to protect them. Also, not having a college education is coercive, and so are fatty foods, which justifies... Also coercive is capitalism, which justifies not letting children buy things (they'll be tricked into wanting more and being materialists).
Right-wing folk object to TCS because they don't understand causality in human behavior. Mindless causes are ok, but not rationally discussable ones. Hence, children have bad theories because kids are dumb, not because their parents mistreat them. And TCS is a waste of time, because children won't understand anyway. Children are dumb, you can see it if you just look around and watch some kids mess up. The solution is to discipline/spank them (notice this is a method that can be applied, unthinking, to any problem). Also, as behavior isn't caused in any rationally discussable way, people who say treating children as inferior messes up their theories can be ignored. Besides, do children even have any theories besides the ones we teach them..? And also, genes cause behavior and being naughty is human nature (but beatings can overcome human nature).
Thanks to Rachel Lucas for the gun link.