They're protesting what that flag represents - at least that's how many people perceive it.
Bad people do bad things. If you're purpose, and those with a similar mindset, is to divide, it's succeeding on a grand scale. Attacking what a large portion of the population holds dear is not the way to their hearts. Maybe your intention is to divide? It's the only logical conclusion I can come to.
You may interpret the flag as a "piece of cloth". Others, view it as a symbol of the best America is and could be, not to mention honoring those who've given their life in honor of it. You're dismissing a lot of people - white, black, or other -that believe in equality and the US Constitution, the foundation of our republic. And, you're giving those truly racist, hateful, despicable people something of substance to justify their propaganda for hate. So, again, if your motive is to truly divide keep on with the status quo.
I will never be OK with kneeling for the national anthem. Anyone - anyone - who does so will lose my respect - period.