It is the band Primus' slogan, meaning that you would say it if you really like primus. they got sick of the slogan after awhile but some people still say it because it's a great slogan, so if you see someone post a comment on a youtube video of primus and they say primus sucks give them an E-high five.
Fan: Primus sucks!
noob primus fan: dood primus doesnt suck fuck u
Noob fan: Damn straight