Hello there,
You can drive the speed you wish to and if you want to follow the speed limit set in game, that is perfectly fine. There is no need for you to go any faster and you are not required to listen to people who tell you any different in game. If they are wishing to go faster than you, they can simply overtake in the correct place to do so that does not endanger you or any other drivers around you.
If you feel that someone is breaking the rules when trying to pass you or is threatening you with insults because of your speed, I would suggest you report them using the in game feature or via our website at: https://truckersmp.com/reports
I feel like what I have provided you is a good enough answer to your question. If you feel that I have not covered anything and have questions, feel free to ask.
If you do not, I will go ahead and move this topic to the correct place.
Kind Regards,
Savage
TruckersMP Support