Who says that? Why should you unite with your enemy?

So what? What's the downside of using a variation of a common license that is not approved of by the OSI or FSF?

Someone other than the target excluded group might not use the software you're offering for free?

Who would get mad if I released code under the MIT license (or some variant) with an additional requirement that it cannot be used to build Web sites the advocate killing abortion doctors?

If it's my code can't I just set whatever conditions I want (modulo the requirements of any prior licenses my code may be bound by)?