Surely the relevant thing in all these cases is intent.
Call it what you will
go back far enough the only time you knelt was in respect of something or someone who you believed had power over you be it liege lord, master, priest or your god. The young man who kneels to propose says by his action although unworthy of you I am asking with respect, kneeling says I am beneath you, or I place myself deliberately in submission for whatever reason.
So kneeling in memory of fallen brothers in arms is a sign of respect, but ill serves the equality cause except in the sense of submission to someone or thing you believe you have harmed. I believe it might be better for sportsmen to find another symbolic gesture, one that does not generate such divisive reactions as that seems to be the opposite of what is intended.