Here are studies that claim homosexual men are less physically aggressive than straight men:

1. Relational aggression and victimization in gay male relationships: the role of internalized homophobia.
http://www.ncbi.nlm.nih.gov/pubmed/18506684
Re

2. Aggression, Empathy and Sexual Orientation
http://www.sciencedirect.com/science...91886905002527

BTW If you would like, you can read the book called Brainstorm: The Flaws in the Science of Sex Differences by Rebecca Jordan Young. She challenges many of the theories regarding gender differences and sexual orientation. She is a sociomedical scientist whose research includes social epidemiology studies of HIV/AIDS, and evaluation of biological work on sex, gender and sexuality. If want more links, please let me know.