Why are girls so ruthless in online dating?

I have a profile on plentyoffish.com. I'm a young 25 year old african american male. But everytime I send a first message to a girl that I'm interested in, I never get a response back. I have a profile picture of myself smiling and positive. Girls always say that they're tired of the different messages they recieve that's full of jerks sending them bad message. I always send them positive messages talking about their interests and even complimenting them on their smile. But no response. Not even at least a thanks but no thanks type message. I think race has something to do with it because I put a picture of a average white guy with my same words and I get responses back left and right from the same females who didn't even respond to my messages! It's crazy. It seems like girls are raised to date every race of guys except black guys. I feel like I'm not ugly at all and have had girls tell me I'm attractive in real life. I feel like I'm cursed being black