It's only because they have decided that they should try to force Theora on people that they are rejecting that solution.
You can still install a plugin to view H2.64 video in firefox. You are not being prevented from that option, Mozilla is just not forking over the licensing fees and having it available by default.
You use of the word forced is hilarious. It is like saying that the first amendment to the US constitution forces free speech on its citizens or that a free neighborhood bbq forces food into people's mouths. Nobody is being forced to do anything. Mozilla decided they didn't want to promote a licence that requires a fee (one that can change and is quite substantial). If you want to use it, you are free to do so.