Does this constitute illegal discrimination against prospective tenants?

To start, I would like to thank you in advance for your assistance.

I am a female currently renting a home with my boyfriend and two other tenants in Illinois. We have collectively decided to search for another rental property within town for the '08-'09 rental year. I have placed calls to several companies and private landlords and recently received a call back from one of the latter. The conversation began normally and he was very enthusiastic and flattering as we discussed his properties, their amenities, and their terms. He stated that of his three properties, one he rented exclusively to females and a second was currently occupied by all females, as well. I inquired as to whether he had co-ed properties, as my potential roommates were male, to which he responded yes, but only after a long and, what seemed to me, a rather uncomfortable pause. He then asked whether I was romantically involved with one of the gentlemen I planned on renting with, and I answered honestly. After another silence he proceeded to tell me that, from a business standpoint, it was unsound practice for him to rent to couples. I was initially paralyzed with, frankly, shocked outrage, but I proceeded to argue with him (yes, in a calm and logical manner) but he began listing all the reasons why he didn't like renting to couples and he absolutely refused to listen to my rebuttals or allow us to examine his properties.

Obviously, neither I nor my roommates now have any desire to have this individual as a landlord, but I would like to know if I have a legitimate legal complaint and what, if any, actions I can take against him.