It is very hard to say what general attitudes are, even in Harry's generation. Hufflepuffs and Ravenclaws support the Gryffindor Quidditch team against the Slytherin - is it because Slytherins are unpopular or because of their previous long string of wins?
Ernie is protective of Justin in COS, but in GOF when the Hufflepuffs think Harry is an attention-seeking cheater they join forces with Slytherins in the 'Potter stinks' campaign. Hufflepuffs and Ravenclaws join the DA in OOTP - is it because they believe Harry, seek to fight Voldemort or simply because they want a better training in DADA than they can get with Umbridge? I don't see evidence that Slytherin House is unpopular with Ravenclaw and Hufflepuff until at least the end of GOF except for the unpopularity that derives from repeated success, regardless of how students feel about blood status.
Ernie is protective of Justin in COS, but in GOF when the Hufflepuffs think Harry is an attention-seeking cheater they join forces with Slytherins in the 'Potter stinks' campaign. Hufflepuffs and Ravenclaws join the DA in OOTP - is it because they believe Harry, seek to fight Voldemort or simply because they want a better training in DADA than they can get with Umbridge? I don't see evidence that Slytherin House is unpopular with Ravenclaw and Hufflepuff until at least the end of GOF except for the unpopularity that derives from repeated success, regardless of how students feel about blood status.