OP banged on the window because she was a cyclist and clearly thought that was fine.
No she didn't. It wasn't because she was a cyclist. It was because she takes public safety very seriously. She's made explicit reference to that.
Would it be ok for someone to get out a car to bang on the window of another driver?
Probably not. I've done it though. I didn't do it because I was a car driver. I did it because I lost control of my temper. FWIW, I banged on their window, shouted that they need to check their blind spot before pulling over and got back in my car. I shouldn't have. I doubt I was intimidating as I was certainly physically smaller than the (male) mini-van driver was.
And glancing at your phone while at a red light is not the same as, for example, texting whilst driving
Legally it's exactly the same. Hadn't you realised?
OP clearly thought being a cyclist gave her some sort of green light (excuse the pun) to behave like an obnoxious twat.
Nope. It has nothing to do with her cycling. It was because the OP wanted to. The cycling aspect was nothing to do with it.
Can you show me where you're getting these assertions from? Maybe I missed the relevant post.
Having a conversation can be just as distracting to a driver
Actually, talking on a phone (handsfree or otherwise) is shown to be more distracting. I worked on computer code which analysed phone conversations from a driver against a driver and a passenger. The conversation with two in the car was noticeably different The driver was much more likely to halt the conversation when their attention was needed such as pulling out of a junction as was the other party. It is these difference that make phone use so dangerous.