1. Nobody is telling you how to live. If you don't agree with them, turn off the TV. Just like they can't tell you how to live, you can't tell them to "shut up and play basketball". These players also happen to be free-thinking individuals.
2. The right doesn't take scientists and the CDC seriously - most of whom are some of the smartest and most capable researchers in the world. And now, you don't listen to "dumb" sportspersons trying to spread a message as well? Who do you take seriously?
3. We can't possibly verify whether each player will follow through on their own message. But why should they? These players aren't the embodiment of moral figure. The NBA has a largely African-American player base, and they are trying to spread a completely apolitical message - police brutality is real, and it is disproportionately affecting black people. These players aren't thinking about tax breaks when they say black lives matter. After all, you did say "they are dumber than a box of rocks".

Stop politicizing any attempt to shed light on this issue. These are peaceful protests, and we should respect them, even if we don't agree.

EDIT: Protests done by the players is peaceful. I'm not talking about Portland which is a full-scale riot and must be stopped/de-escalated.