As evidenced by the links you supply Threeb, beaner
is present, with various meanings, in Wiktionary, the Urban Dictionary and WordNet. It's also listed in various slang dictionaries. However, I couldn't find it in any standard dictionary edited by lexicographers, which counts against it.
What counts in its favour, and eventually persuaded me to accept it, is the fact that it has so many
As a derogatory term for a Mexican, it seems to be better known in some parts of the US than others. An article
in a Michigan student newspaper commenting on plans for a coffee chain to change its name from "Beaners", argues that "the racial slur 'beaner' is simply much more prevalent in California and on the West Coast than it is here in the Midwest". And a book in Google books feels it necessary to define the word: "so-called beaner raids, beaner
being a derogatory term for Mexicans" (Operation Gatekeeper
by Joseph Nevins, 2002).
The baseball usage seems to be much rarer than beanball
(which is already a Chi word). Google gave me 851 hits for the quoted phrase "throw a beanball", whereas "throw a beaner" got only four.
Apart from the meanings already mentioned, I found a line in the film script for Donnie Brasco
that implies beaner
can mean a hundred dollar bill: "EMPTIES his wallet. Lefty takes it, folds it into a ROLL. Puts the hundred on the outside... LEFTY Don't be carrying your money in a wallet no more. Wiseguy got his money in a roll, like this. Beaner on the outside." But I couldn't find anything much to support that usage, so it must be a very specialised piece of underworld cant, if not a nonce word for the movie.
Also in the highly specialist zone, it seems a train of the B.N.S.F. railroad can be called a beaner
. These obscure usages don't really count for anything, but I hate to waste the fruits of my researches.
I think the word is a borderline case, but I will allow it.