Man this is a hard one. Being a male between 19-25 driving a red sport compact, I definitely understand why that sucks. However, insurance is a business, and the rules of fairness don't really apply to them. Companies discriminate all the time, whether it's in hiring or pay or whatever. I mean, people with college degrees typically get paid more than those without, so is that education discrimination? Also, insurance companies, like most other businesses, can choose not to take customers. I think this is just a fact of free market economies.
For auto insurance, it's not so bad. Health insurance, though, I think these business practices have really adverse affects on treatment.