The anthem and "saluting the flag" are already political ploys so I see no problem kneeling in silent and peaceful protest. If you really want politics out of the game save the anthem for international competitions and eliminate all the military pomp. 

If you really want to support your troops, demand that they don't get sent off to unnecessary wars of choice. Demand that those who sacrifice life and limb and mental well being are taken care of for life when  they return with PTSD or missing body parts. Demand that the Commander in Chief stop using dangerous bluster that is escalating to another senseless war. Wrapping one's self in the flag is not supporting troops, it is not patriotism, it is blind nationalism. 

Give us a break and go right to playing ball and skip the pregame propaganda.