It's just that there are other 'universe constants' like that which pop up in unexpected ways. For example, there is a corollary to "all teasing is affection" which is "anything done out of affection has no negative consequences." So, since all teasing is affection, and all affection has no negative consequence, John can give Cam a lemon to use on Rodney and it's okay. Or Rodney can slip John a mickey and get him to clean his room without anyone getting really upset. or, you know, the team can disobey orders and return to Pegasus without approval, and everything is fine in the end. It's really quite Romantic, and that romanticism underlies everything. It's hard to make realism stick.