"No-Homo" is possibly one of the most unattractive phrases an guy could ever say. Saying this means:
1. You're okay with marginalizing a huge group of people
2. You're immaturity is through the roof (seriously, I thought when I graduated high school these stupid things would be gone)
3. You're uncomfortable with youself, who you are, and expression of emotions.
When I date someone, I intend for the relationship to be an "equal partnership." A guy saying "No-Homo" is saying, "Hey, I'm insecure with my masculinity and am going to ask you to fall into stereotypical feminine roles in order to boost my low self-esteem as a man."
I made this observation of a group of people after knowing these things were true, and finding that the common factor was subtle but very-much-there homophobia. If people don't fit into the exact gender roles and ideas of sexuality that they have come to know, it scares them, because where does that mean they fit in?
This seems to me a quick and simple litmus test to separate guys I have zero desire to date from guys still in the running. I prefer emotionally stable men, ones that won't intrude in my life but rather compliment it. I don't fit a wide range of feminine stereotypes, so I need a guy who is comfortable with that. I have no desire to change fundamental characteristics of myself for another person.
"No-homo" == no chance.