In 10 second clips. Thought there was a fair use clause that permitted that sort of thing?
It's a complex area of the law. Is his youtube channel monetized or does it contain ads? If yes, probably not fair use. If no, the questions just keep coming. The percentage of the material used is probably more important than the length of any individual clip.
But if he wants to get Google/Alphabet or whatever entity now owns Youtube to ignore a takedown order, he probably needs to be willing to enter into an indemnity agreement with them and show financial capacity to cover damages and expenses. Because the bottom line is that it would be a fact intensive inquiry at trial.