Yes they're cute. Yes they helped the Rebels. But look at it this way:

They tried to eat Han Solo. EAT HIM. What creature, other than a rancor or something, tries to eat people?? They may use their cuteness to divert people, and then eat them....

In the RETURN OF THE JEDI, at the end, they were having the party, right? They're playing drums and such. But look at what they're banging on....Stormtrooper helmets! These creatures seem like they are very sinister little things towards humans, no matter what side they are on.