who the asshole who told you that??.. and you are an asshole to believe any shit without checking if it's true or not 
Mohamed PBUH only said dog's mouth is not clean and we must wash any bowel we eat from very well if a dog eats from it or licks it.. also he said that there must be a need to have a dog like helping you in hunting, farming, guarding.. etc.. so yes it's not very good in islam to keep a dog as a pet like i do.. i know this well and i dont rearrange any texts to suit myself..
Islam forbids Muslims to keep dogs, and the punishment for that is that the one who does that loses one or two qiraats from his hasanaat (good deeds) each day. An exception has been made in the case of keeping dogs for hunting, guarding livestock and guarding crops.
It was narrated from Abu Hurayrah that the Prophet said: “Whoever keeps a dog, except a dog for herding, hunting or farming, one qiraat will be deducted from his reward each day.”
It was narrated that ‘Abd-Allaah ibn ‘Umar said: The Messenger of Allaah said: “Whoever keeps a dog, except a dog for herding livestock or a dog that is trained for hunting, two qiraats will be deducted from his reward each day.”
It is not permissible to keep dogs except for hunting or guarding livestock and crops, and it is permissible to keep them for guarding houses so long as that is outside the city and that
there is no other means of guarding the house.