I think you are attributing to malice what is probably just laziness. It is fairly common for modern websites to drop the ball on support of some browser or other. I doubt Microsoft as a corporation made a deliberate decision to support IE and Firefox but not Chrome or Safari or Opera or whatever.
It's one thing to not test a site in a particular browser and to just put up an unobtrusive warning saying that some things might not work perfectly. It's quite another to actively block access based on the user agent string.
