The question isn't whether it's harmful. Lots of currently legal things are harmful. The question is whether you think you have the power to tell a supposedly free person what he can or cannot put into his body. Telling him that he cannot is imposing your beliefs onto that person. You might as well be telling him what religion he can or cannot believe.
“Liberals deny the existance of objective truth and objective right and wrong. When these things are not (seen as) objective, they are defined by the individual, and inherently conflict.
Therefore, what is “right” and “true” is determined by who obtains and uses the power to impose their “truth” on others. Government therefore becomes GOD to them.”
...from Mr.B