Well, my personal opinion is a simple one, and its based on experience...when your in the air, the only judge ATC have of your flying ability is your RT. Simple as that. Talk rubbish on your initial call to enter a controlled section of airspace for example, and they WILL think twice before clearing you through.Be as professional as you possibly can, and your will recieve respcect back via the airwaves.
That point was given to me years back by an air traffic controller, and has been shown since to be a true one.
You would feel a loss of personal pride if you willingly allowed your flying skill's to go to rat****, so why is RT any different?