I agree. I think a more accurate representation is "system favors the house". Which is what probably irks the day traders the most. Rigged insinuates illegality, which obviously is not the case.
That's true in the gaming industry as casino patrons knowingly pay for entertainment services provided by the owners. The charges come out of patrons' wagers as agreed.
Let's decide that the market is for working adults and no place for fun'n'games. I enter the market with my eyes open and make my choices of my own free will, I'm a satisfied customer for what I buy and I'm grateful for my customers' business when I sell. If the market is 'rigged' at all then it's us guys buying and sell who're doing all the rigging. I mean, we're the guys who set the prices and all.