No, anyone well versed in science knows not to make assumptions without data to back it up, like you're doing here. Show me a study where they've found a serious, credible causal link between cannabis smoke inhalation and any kind of ailment that isn't psychological.

You can't. I've looked.

I'm not saying it isn't harmful. I believe it almost certainly is, on some level. But without data to back it up, that's all it is. A belief. Not a fact.

Extensive study has not been done on the subject, but the preliminary work shows that if there is a link to physical damage to organs like the lungs, it's a small one. Here's a great summary from one example:

Although marijuana smoke contains a number of carcinogens and cocarcinogens, findings from a limited number of well-designed epidemiological studies do not suggest an increased risk for the development of either lung or upper airway cancer from light or moderate use, although evidence is mixed concerning possible carcinogenic risks of heavy, long-term use. Although regular marijuana smoking leads to bronchial epithelial ciliary loss and impairs the microbicidal function of alveolar macrophages, evidence is inconclusive regarding possible associated risks for lower respiratory tract infection. Several case reports have implicated marijuana smoking as an etiologic factor in pneumothorax/pneumomediastinum and bullous lung disease, although evidence of a possible causal link from epidemiologic studies is lacking. In summary, the accumulated weight of evidence implies far lower risks for pulmonary complications of even regular heavy use of marijuana compared with the grave pulmonary consequences of tobacco.