I had wondered the same thing when we saw it on Hwy 280 on the way to the Morgan State game. I asked a staff member in Gopher Fan Relations. The scoreboard is on during all Gopher athletic events in the Stadium Village area. The point is to create festivity when people are heading to games.
The glow is a little crazy when it's hazy and snowy out but I think their aim is on track. It's nice to have that outside display when walking from parking lot to arena during a blizzard. As for creating light pollution as the letter to the Daily talks about, it's a bunch of hogwash. You willingly chose to live in the middle of the city, within a mile of the campus. Get over yourself. As for budgets, while there should be some oversight, the athletics department brings in a lot of revenue (a lot of it from private donors who want their money to go specifically to athletics) and should be allowed to use it to promote the program. As long as it's not a safety hazard. Let it be.
Also according to said staff member, the scoreboard is on any time they have events at the stadium, which is pretty much daily. Part of the agreement was that the stadium would be used for private parties. They hold them in the indoor suites as well as the DQ room.