Another eventful ride home...

Upon my journey, I was riding down the bike lane along backed up traffic, minding all the usual precautions in such a situation. Down the line of cars, a sedan decided to make an abrupt change across the bike lane and into a further parking spot. This action was begun as I was next to the rear wheel of the car, continuing forward along parked cars before the open parking spot, forcing me into a bottleneck with pinning implications. This is when I, in my typical fashion during such situations, gave the side window a firm slap with an open palm. Not a Ulock, not a fist, but an abrupt slap. (also note, I did not slap the car for fun, and I was already along side the car and being bottlenecked as everything happened)

Considering that cars use horns to warn other drivers of causing potential harm, this seems like a sensible method to bring it to the drivers attention that they are doing something wrong. If nothing else, they will stop because they think they have hit something, and caused damage to their own car with no regard to the outside world. Moving on...

After the slap, which stops the car, I manage to sneak through between the front corner and curb. As I look back I see the gentleman getting frustrated and screaming through the windshield.  I decide to stop and speak to the driver, I approach the drivers door, Mindful to keep it from being opened. Transcript as follows:

Driver: You didn't have to hit the window. 

ME: You didn't have to cut me off. 

Driver: I didn't see you. 

Me: Well you should pay more attention. 

Driver: You can't do that. You'll be in trouble, I'm a cop. (proceeds to fumble for and flash his badge)

Me: Well then you should have known better to look before you do something like that.

Driver: Just move along, you'll be in trouble if you do that again.

At this point I continue to ride with the driver assuming little responsibility. Usually it ends up with an apology of "I'm sorry, didn't see you" and me politely reminding the drivers to look out for us bikers. I'm not trying to make a matter out of the gentleman being an officer as we all make mistakes, but of the empty threat of me being "in trouble" next time. 

My question is, what do you propose to do in such a situation to preserve your safety?

I think a firm slap is a safe way to bring warning to the driver of the inherent danger they have caused. I am not trying to cause harm to the car, but prevent it to myself. I do not have the law in front of me, but I would assume striking a vehicle is an illegal activity. But in lieu of a horn, I think it is a passable offense. 

The driver, while maybe right in saying I could "be in trouble",  he didn't look at the other side of the situation and understand why I slapped the car. I suppose I could have stayed and questioned him further as to what I should have done to preserve my safety, but preservation of freedom seemed to take a larger roll.  I'm sure that would have been a most enlightening response.