AIBU that road near my house is not motorway replacement

[FlowerSour]

Another car related AIBU but different this time. And more light hearted

Motorway near me is closed and the road I have to use multiple times a day is the diversion. The road that is the diversion is 50mph. I always go at 50mph if the weather is fine yet ALWAYS (or quite a lot of the time) have some arsehole seemingly a foot away from my car, then overtaking me and speeding off into the horizon. Normally with clouds of exhaust shit wafting around after. People seem to think that because the motorway is 70, it's totally okay to use the diversion at the exact same speed!

I've only been driving less than a year so six points would lose my license.
Hence why I will not go faster even with a modified, petrol monster trying to apparently become one with my car. And obviously from a safety point of view...

So AIBU for doing 50mph when 50mph is the fucking speed limit? And that just because the motorway is 70mph, the diversion is NOT? (50mph signs very clear!)

Stick to 50 and if an opportunity arises for them to pass you slow down to make it easier for them. I hate tailgaters, the sooner they are away from me the better. Don't get angry as the only person you wind up is yourself, as a new driver that's not a good idea and they don't give a shit.

^ obviously 30 years of driving has mellowed me!