So much this. The number of entitled drivers that think the left lane is their personal lane to go 90-100MPH in and that every other car should move out of their way these days is bonkers. Especially here in San Diego. To me a light flash is a good indicator to slow and match the speed of the person to my right because they must be trying to warn me of my unsafe speed, right?
I've been doing 85-90 and in the left lane and had people tailgate and flash lights at me I've even had multiple people do this in the damn carpool lane when there were cars in front of me like they were expecting the entire carpool lane to empty out for them to go faster.