First, the female workers need to do the reporting. You could serve as a witness if asked, though.

I think if you go around reporting these guys and acting all offended, they will turn their nastiness on you. You need some allies among the women and then maybe schedule a conference with HR as a group. Then it is up to HR to offer the offenders some guidance.

In the meantime, I would avoid any gatherings of these guys such as the break room or around the water cooler. I would just politely and discreetly make myself unavailable to participate in their banter. Just walk away or make an excuse, doesn't matter.

Good luck.

This appears to be a difficult situation and I believe that your advice is spot on.

the women in the workplace are never targeted except for that one incident which I reported.

it's mostly in their language and jokes, which also isn't quite common but still it grates me.

I can't avoid gatherings of the group because there my team and we work in a lab together.

Have a chat with him. Tell him you are uncomfortable with the sexist banter, and you think it is inappropriate. Ask him to approach the other guys. If they've grown up with this kind of behavior, they may not even realize they are doing it.

This is a tricky situation. If you are not close to anyone, this will not work, and he/they will turn on you.

for a while he would warn the others that the walls have ears but that didn't last long really.

I think you have done all you can do personally. A little hard core education has to come from the company itself. And the move to do so has to be initiated by the women.

I mean at least I started a dialogue in the company about it.

If you're going to call yourself a male feminist, you're going to have to accept that you're going to be put in these kinds of situations. For every man that chooses to side with sexism, another woman has to suffer out of his selfishness.

You're Indebted to women by calling yourself a feminist and you have to own this responsibility as being a man. If you value petty social relationships over pushing our agenda then you're not a real feminist, and should stop posing as one.

but I'm not losing my job over it.

I have a woman that I put above all others and I will keep a roof over her head.

I think being the best example possible of what we expect from ourselves and others is among the most effective methods of allowing others perspectives they may not otherwise have have access to.

Speak out when you can, but being an example is the best avenue.