The Libraries internet is controlled by public opinion, because everyones tax dollars are paying for it. If you don't like it, make a change and go to one of your city's public meetings and petition for change. The Library is not out of line.
If you want to do what you want, like go on message boards and what not, either pay for internet at an internet cafe, or find some really cheap DSL package. Milwaukee I know is offering some at 9.95 a month.
Thats about all you can do.