That should be "beside the point", not "besides the point". By saying "beside the point", one means that something is literally on the side of the point; in other words it is not related. However, "besides" means "moreover", "furthermore", or "also". Rather than an expression of physical direction, as in "beside", it is a transitional preposition used in speech to introduce a new topic.
Look guys, I know how to bitch too!