Fairly common knowledge. Even portrayed in movies like Kuru and Seven Years in Tibet. Unfortunately the whole thing has been wrapped up in lots of misinformation. The Tibetans have both accused China of atrocities and claimed that they didn’t happen. Outsiders looking in on this could argue that they were trying to appease the Chinese to maintain the paltry religious autonomy granted by the Seventeen Point Agreement. Here is a link to a PDF from the Tibetan Bureau in Geneva listing their atrocities. It is worth noting that even these claims are impossible to verify. The Chinese government has worked tirelessly to scrub the world knowledge base, and most search companies are more than willing to cooperate with such large governments with huge resources. Additionally, sensationalism is equally attractive, meaning it is easy and tempting to over report and exaggerate war crimes.
But the simple fact remains that May Zedong openly opposed religion and claimed that his annexation of Tibet was a “liberation” from what he called “religious oppression.”
Is this just an end run advertisement?