Riot did (and can excuse themselves with) Christmas skins in their early years because it's not really (nor did it start out as) a Christian holiday.
The Christians took Saturnalia (a grand roman festival) because many people were already celebrating at that time of year.
Jesus wasn't born in winter, gift giving and being nice started was a Roman pantheon tradition, and bringing in a tree during the cold season was a pagan thing.
Santa Claus (St Nicholas) is more mired in warpings and retelling of history and fiction that there's no way he can't be non-secular public domain.
Judaism however, is a real world thing. People believe in it, go to temple, and follow its tenants.
To put it in perspective, Ocarina of Time's Gerudo tribe originally had Islam's Crescent and Star symbol. It was removed for the all the re-releases though, cause IT'S A BAD IDEA TO USE SOMEONE ELSE'S RELIGION FOR MONETARY SHIT.
http://en.wikipedia.org/wiki/Saturnalia
http://zeldawiki.org/Gerudo_Symbol
http://en.wikipedia.org/wiki/Santa_Claus
TL;DR
Santa and Christmas are public domain. Judaism has actual people who worship in it. There's a reason any new Winter skins are Snowdown.