I think the best argument against git is to use mercurial for a few months. It has exactly the same functionality but a nicer and more streamlined interface, especially when it comes to branch management.
$ git help commit | wc -l
506
$ hg help commit | wc -l
59
$ hg help commit -v | wc -l
96
Also, git currently has 169 subcommands by default, vs. mercurial's 50 (more available as extensions though).