This advice and all the supporting comments just seem to me like a bunch of people who have operate using a very basic set of rules for human interaction because advanced concepts are beyond them. Be a good sport, respect your opponents and their fans. Check some of the posts on the sub, if its they sort of sub where outsiders aren't welcome, leave. If they're the sort of sub that welcomes discussion, post.

As an Aussie fan I was ecstatic when I went to my first Ravens game at the Bank and there were Steelers fans next to me and a bit of friendly banter was going on. You don't want to get like English soccer where the fans have to be separated by fencing and security otherwise they brawl.