Do you flash your lights to warn other drivers of a cop ahead, waiting to molest them?
If not, why not?
Would you alert your neighbor to a burglar climbing in her window?
Would you let a couple walking in the park know you saw a guy with a stocking over his head hiding in the bushes waiting to ambush them?
If you don't warn other drivers is it because you know the other drivers might be "speeding", so they "deserve" to get stopped?
What if your neighbor has a wall-sized television that you envy? Is it OK for that to be stolen by the burglar?
What if the couple in the park are rich and have "too much money"? Is it OK for them to be robbed?
What if the thieves in each case don't stop at theft, but attack in other ways as well? What if the burglar is also a rapist? What if the guy hiding in the bushes is also a murderer? What if the cop has "officer safety" issues and is prone to be trigger-happy when frightened by an unexpected move or by the presence of a gun that isn't under his control?
Bad guys are bad guys, and I am happy to warn others of their presence.