You can never win an argument against a leftie but what you can do is win over the people who are listening on the sidelines and are uncommitted. The trick to this is to use logic and facts to beat your opponent into submission and then finish off with a rhetorical shiv. To succeed in this you need to get out there and practice. Take on your opponents without fear of being beaten. If they do beat you in an argument then you will have plenty to learn from for next time. You don’t get skilled at this stuff by sitting at home and yelling at the internet.
The other weapon that you need is a good amount of those pesky facts to smash them with. One of the favored myths propagated by the left, and I might even say their most favored, is this idea of patriarchy. Specifically, white male advantage or privilege as they refer to it. Courtesy of the good Chateau I discovered a marvelous rebuttal to this core leftist policy.