Literally, bashing is a term meaning to hit or assault, but when it is used as a suffix, or in conjunction with a noun indicating the subject being attacked, it is normally used to imply that the act is motivated by bigotry.
Karen Franklin, in her paper "Psychosocial motivations of hate crimes perpetrators" identifies the following motivations for bashing: socially instilled prejudice or partisan conflict; the perception that the bashing subject is in some way contrary to, or in offense to, an underlying ideology; group or peer influence.
[1] One of the more common uses of the term bashing is to describe assault or vilification of people perceived to be homosexual.
In cases of non-physical bashing, the term is normally used with the intention of having a pejorative effect on the identified bashers by comparing them to perpetrators of criminal assaults.
These terms are used to imply that the criticism of these groups or individuals is excessive, too frequent, uncompromising, or inappropriate.