It's funny that you consider that study to be the claims of scientists. Any academic would disagree with you. The sample size is too small, with too many statistical outliers, no control is present, and no variable was isolated. To draw a clear conclusion from that data is laughable and subject to confirmation bias. I had previously seen that study mentioned, but I have also seen numerous sources discredit the methodology of that study.
If you actually care about studies that follow the scientific method, thereby providing reliable, replicable results, check out the literally THOUSANDS of academic studies that disagree with you.
In regards to your uncle, I don't mean to be insensitive, but you're missing the point. There is no known carcinogen present in cannabis. The use of cannabis did not cause his cancer, the act of inhaling the byproducts of crude combustion did. If you were to smoke ANY plant, it would increase the risk of lung cancer. This isn't because the plants are carcinogenic, but rather the byproducts of combustion are. If he had used a vaporizer or ingested the cannabis instead, then he would not have developed the lung cancer. Many of the compounds present in cannabis have been shown to inhibit tumor growth and destroy cancer cells.
In short, you're wrong.