I don't think it's hate but it's more about the costs of supporting a totally new environment. DreamHost was born and has hired, trained consistently people with Linux/Unix, Apache, PHP, Perl etc background. Adding a totally foreigner technology at the time would have been a bold move. Nowadays, with .NET available on Linux maybe it's a little less of a bold move but still a pretty bold one.
One way to change people's mind is to show there is a market for something. I bet if all of a sudden there were dozens of tutorials published on how to run .NET applications on DreamCompute, someone may look into the costs/advantages of adding .NET to VPS