well as far as I'm concerned there are 3 things one could be refering to when using the term satanic/satanism
1)Satanist from an uneducated standpoint: this is the satanism christians and the like often refer to, they often insist that it is a cult which ingauges in animal sacrifices and baby slaughter. it is largely used as a scapegoat for anything which they consider evil for example they have blamed the recent abductions of children in haiti on satanists, these cults do no exist, they are fictional and are merely christian scare tactics
2) theistic satanism: the beleif the god and satan are backwards, the reason they beleive this is because the story goes the satan(refered to a lucifer) was an angel in heaven who defied go and was cast out of heaven, they beleive that he defied god because he disagreed with his methods such as flooding the entire earth and killing everyone, and god does seem like a bit of a tyrant when you take into account that he is going to damn people to hell simply for not beleiving in him
3)LaVeyan satanism: atheism accompanied with a philosophy, founded by Anton LaVey, satan is symbolic of mans carnal nature, no beleif in a high power or devil what so ever.
now onto why some people will call the catholic church satanic.
the term satanic people are using in reguards to the catholic church is the 1st term I gave, the people who are refering to you as satanic are looking for a scapegoat, probably because alot of catholics are pretty fundamental when it comes to their religion and the bible has some pretty horid things in it. the catholic church insists that gay's are immoral and stuff like that, modern day society is more accepting and doesn't take kindly on discimination, this is seen as evil, lastly I forget which church it is but one features an inverted cross, many associate this with satanism, in reality it is in refrence to peter (I think) who insisted on being crusified upside down because he did not think himself worthy to die in the same way as jesus.