I don't really see the problem forcing people to use another browser. They did not complain when MS installed the Browser directly into Windows 95 and started using it, now they download Gigabytes of movies each day and when you tell them "you will just get this movie if you click on these twenty links" they do so without question.
When you then tell them it "could" have been that their browser left trails about them left and right while beeing vulnerable to dozens of unfixed errors, they mostly just shrug and carry on.
If they complain about you asking them to install another browser you can then just shrug because they were able to install ten or more filesharing proggies to get their MP3s, Warez and everything.
I think it is not bad to force people to kind of inoculate themselved against the dangers of the internet.
That was the harsh version.
The mild version is: EXP does not like M$ Browsers so he doesn't want to "fix" parts of the page to suit that browser - and usually the reason is M$ not implementing W3C or other commonly accepted standards - which means non-conformity. As long as EXP sticks to standards nodoby can complain I guess
I'd start complaining once neither Firefox/Mozilla nor Opera work anymore for those two browsers usually are very compatible and standard-conform.