@KenjiOgiwara of course we should, and demonstrably are, allowed to talk about it.
The reason it got a few backs up is it has been constantly insinuated up to this point that people will be forced to kneel with lots saying that's absolute bollocks. When it was proven to be bollocks there is still an insinuation that this is super surprising in our world, even though I'm not aware of a single example of the opposite happening and someone being forced to make the gesture.
Peer pressure is another thing. Let's be honest all most celebrities will be doing is making a financial calculation as to whether or not a certain position would hurt their careers. There is always going to be public opinion one way or another, personally I'm glad it leans towards supporting peaceful protests.
It's not one sided anyway, as you'll know from the massive amounts of abuse Kapaernick took, including from the president and NFL owners. Has any high profile figure at all had a go at the drivers that didn't kneel?