"If I want to release my software under a BSD licence, it's not free software because RMS doesn't think it is."
I thought the FSF had publicly stated that BSD licenses were compatible with the GPL, and thus "Free" software. I wouldn't be surprised if rms wished the software were more free (in his sense of the word), but I don't recall him ever saying it wasn't free.
They do consider the modified BSDL to be both a Free Software license and compatible with the GPL. There are other licenses which are not compatible with the GPL, such as the original BSD license (with the advertising clause), yet they do still consider them to be Free Software licenses.
I thought the FSF had publicly stated that BSD licenses were compatible with the GPL, and thus "Free" software. I wouldn't be surprised if rms wished the software were more free (in his sense of the word), but I don't recall him ever saying it wasn't free.