YouTube, GodTube and stuff - how to determine if a clip is legal?

If you found an .mp3 uploaded by an obscure nickname, it’d be pretty easy. However, most of the material seems to be videos. I suppose if many of them were illegal, those “Tubes” would be shut down and sued out of their last shirts. However, I don’t know where people get those videos from - like ripped from a DVD, recorded from the TV and so on. I know there’s plenty of religious stuff there and recently my grandmother has come asking to see some as a priest gave her some names to look for, but I’m at a loss as to how to determine the legality of the video being there and I wouldn’t really feel great looking at it, “until I know for sure it’s illegal.” So how do I make sure?

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