The term Sacklicker is considered to be one of the most derogatory references that can be used toward one heterosexual male from another. Its origin was most likely the Northwest United States around the year 2000. It is most often used as a trump in place of other slang phrases such as "He is a piece of crap motherfucker". This form of slang is Gutterslang.
A Sacklicker is considered the lowest form of male life and is even lower than a cocksucker.
Other uses of the term may refer to oral sex such as a fellatio limiting the derogatory use as noted above.
"That Sacklicker sucks dog balls"