So I have been pondering this question since it was posted. I think we are at a point where even the most patient and optimistic of us Mason fans can see that there is some cause for concern. Here are my honest thoughts on how to have the outcome that is most beneficial to the future of Mason Men's Basketball.
Start by getting the biggest group of like minded individuals together that you can assemble. Total the annual donations of everyone in the group. You could even take Jollay's idea and add a membership fee to add to the total donation value. Hopefully this number will be significant enough to show how serious the issue is. Make the group official in some manner, by having people sign on to it's mission in a formal manner.
Call the group something positive like Fans in Support of Mason Men's Basketball. Come up with a mission that all in the group support. Make the mission positive in nature, too, like to ensure the prolonged success of Mason Men's Basketball. Avoid something with a goal of getting a particular person fired. Also, don't threaten things, at least not in the early stages. If you do get to that point, you have to be ready to go through with it, and know what your next step after that would be.
Be sure to professionally state your case. If possible, be prepared to back it up as much as possible with data, game clips, etc. Specify the problem as you see it as a customer/supporter of the program. When you are doing so, I would be very careful to not specify the solution. Whether you are dealing with the Coach or the AD, they are the professional at doing that job. If they ask for your opinion on that, then provide it, but don't go there unless they ask your opinion. While we all like to Monday morning quarterback the games, you will lose a lot of credibility if you try telling an expert how to do their job. Give them the opportunity to address your concerns.
It will take a little time to get things moving, so you could start now. If things get better the rest of this season somehow, well, at least you are organized for the future. If not, you have this season's data to back up your point.