If they pay for a season ticket they have every right to go to every match, just the same as you do. They also have the right to express their support, or otherwise, in any way they please as long as it is legal.
What gives any blue the right to impose their 'let's get behind them lads' attitude on any other blue. If you want to go to the game and give Benitez and his team your support, that's fine and it's your decision. If somebody else wants to go to the game and express their displeasure, that is their decision .