No why would anyone put video on a blockchain? A blockchain is just a very, very slow database, this would be horrible.
Our blockchain is used for the cryptocurrency TUBE. The video data is on IPFS, it's decentralized storage sort of like bittorrent but more advanced. Everyone on bit.tube is a storage node instantly, it works automatically in the browser. That's the magic trick, you don't have to download anything.
As for your question, videos can be unpublished when they violate copyright, we have to abide by the law, we don't want to end up like the pirate bay. But this is a centralization and censorship issue so later we want to put the community in charge of copyright review & reports/disputes so that part is more decentralized. But we have to build that in the next months.
These are basic questions though so please check the FAQ on reddit
https://www.reddit.com/r/BitTube/comments/8lk12r/faq_frequently_asked_questions/ . If you have any more question let me know.
So, if you're against decentralization and censorship, why does your moderator keep removing thumbnails?