Opponents of marijuana are they correct or using scare tactics? Does the higher concentraiton of THC actuall?

opponents of legalization claim that marijuana is more potent now more than ever(meaning there is a higher concentration of THC). Now there must something im missing but isnt that good thing health wise? It means that we have to smoke less to get a desirable effect (smoke in the lungs has been the only proven health hazard to smoking marijuana and even thats iffy). So im just wondering are these opponents stabbing their own feet? Or are they naive enough to think that in the 60's people didnt get blazed out of their minds but only stopped after they smoked enough unrelated to how high they got? Does anyone see what im saying? Or is there something im missing?