I don't know for sure why the downvote, but maybe because Thailand is a place where you can be imprisoned or exiled for criticizing the (late) king. It's not hard to imagine somebody on HN might not be cool with somebody supporting that sort of enforced devotion.
The user is being downvoted because he brought up an unrelated argument that contributes little to the discussion. The original complaint was being forced to stand up and pay respects to the late king. Not whether people liked/disliked the memorial.
It's akin to a debate about whether Apple was right to push copies of U2's albums onto all iTunes users [0], and someone chiming in with, "But I don't mind U2!"