"I do believe that there was a case similar to this one also that was posted on this board, where the opposite ruling was upheld because of the widespread use of the term in question."
Yes, if you actually read the case to which I posted the link earlier, they discuss the "aspirin" trademark, which was originally owned by Bayer. Other former trademarks include zipper, escalator, cellophane, nylon, and many others. Whether a trademark is subject to "genericide" can depend on the enforcement record of the mark. Garry's question about an obvious grammatical derivation is also asked and answered in the same case. Considering that the decision was rendered less than two weeks ago, "Realtor" is not going to be considered a generic term anytime soon.
Besides, a vendor vends.
What does a realtor do? Realt?