It's a stand against racism, sexism and homophobia, they've said so on numerous occasions, every single person should be for it, I'm not sure why people are against it.
At the end of the day, no person should be abused or tormented be it in real life of online due to a characteristic of the way they look, or due to there personality. It's pretty fucking simple. That's a message pretty much everyone should be on board with, It's a simple 8 second gesture. If you're against it, if you're booing it, if you think it's wrong, you're the people they're trying to convince, and part of the problem, and need to educate yourself, and get out of you're little bubble.
In regards to the "whole of the UK is racist" thing from a few pages back, I disagree slightly with it, I don't think (atleast where I am in Cornwall) that people are openly racist, IE they're could have a normal conversation with a person of another race and not really think twice. Personally I think a lot of people are just ignorant to the fact that some of there thoughts processes and discussions are brought from systematic racism from years gone, and arguably these are the sort of people that need convincing the most, more so then the bigot who actually do shout the bile.
So by continuing the taking of the knee, and keeping this stand at the forefront of there mind, these people slowly get bought round, even people like Calm will one day, as if he doesn't he will be in a very small minority.