So all the people that now try to invoke the streisand effect against them are not even touching their claim, however valid or invalid or may be. If anything, they make the hashtag more valuable for advertisers.
This reminds me of incidents in the past were colors (some special shade of magenta, Deutsche Telekom) or letters (greek alpha, Canon) were trademarked, apparently without much discussion. As I understood it, the reason was that a trademark does not forbid general use by the public. It "only" forbids using it as brand identifiers and for advertising.
Whether hashtags can actually be trademarked is of course a different question. But I don't see how it would be more crazy than trademarking a color.
[1] https://twitter.com/EdmondActive/status/761406212122431488