This rumor started as an anonymous comment on a ZeroHedge article that they ran with.
Until we see some better proof towards this rumor, it should be taken with less than a grain of salt. For every rumor in the crypto world that turns out to be true, there are hundreds of rumors who's only purpose is to assist in a pump for profit. Spreading baseless information is what pump groups do.
Looking at it from another perspective, what reason does Facebook have to accept Litecoin? Who are they trying to appeal to, what market are they trying to attract? I just don't see it happening.