They call that one the strawman argument.
a strawman argument picks a weak, less defensible and largely irrelevant aspect of an argument and focuses on that as opposed to the main relevant point of the argument which is generally a strongly defensible position. This strawman is thrown out by individuals who realize they have no chance of arguing against the previous point and they hope to change the argument in a way that provides them more room to maneuver. As far as I’m concerned, you have thrown out a strawman by claiming strawman because you know that you can not counter my previous point, that the promotion of drug addiction is harmful to society and the individual. You may as well have pointed out a spelling error.