the context is "react" in the title of an internet video.
slashdot did not misunderstand anything.
Maybe you think that the intent was merely to protect their video titles.. well, duh, that is the intent. the intent is to suppress anyone else making react(in the title) videos for youtube or other streaming sites.
if you think that is fair use of trademarks then.. well, good luck. but don't post your reaction to this online in a video.
yeah, so sure you can still make a book called Parents React to Slashdot, though I'm still pretty sure they would sue you for it.
it's fucking stupid and it's just internet fishing at it's worst right now. whats worse is that they're claiming this pretty much after the fact that youtube is already filled with thousands of reaction videos and were filled before they started making their stuff too.
it's like coca cola co. trademarking "refreshing".