As a discipline, philosophy struggles with the numbers of women in the discipline. While this doesn't necessarily lead to misogyny, it does establish that you are correct that philosophy is a male-dominated environment. (This article gives some evidence and some speculation as to why)

The other aspect is that historically most men had attitudes to women that would seem sexist now. To take the example of Aristotle, he lived in Athenian democracy at a time when only 20% of the population (free men) were considered citizens. A lot of philosophy from the past contains views that seem discriminatory now, even when this seems to contradict the message of that philosopher.

To avoid giving a completely negative impression of a subject I love, a few female philosophers: Philippa Foot, Simone de Beauvoir, Rosa Luxembourg. (there are more, but admittedly not that many) There have also been a lot of male philosophers who were much more enlightened about women, John Stuart Mill being the first one who springs to mind.

Summary: It's a problem for philosophy now and has been in the past, but I can't find anyone who can give any evidence beyond speculation (some of which is a bit sexist itself) as to why philosophy should be any different to any other forum for people to give their opinions.