Most Christians would say that they represent the cross. On the other hand, we've got symbols to represent symbols.
I don't know a single Christian who believes the Christmas tree has anything to do with the cross. It's a pagan symbol of the hope of eternal life which was co-opted and Christianized.
OTOH, a hannukiah (aka menorah) actually is a religious symbol. It seems the Rabbi was comparing apples to oranges and got himself (and Chabad, a wonderful Jewish organization) involved in an unnecessary brouhaha.
Really? I didn't think a tree represented anything other than a christmas tree? Does a fence post also represent a cross?