I don't think anti social behaviours are ok in any breed, big or small, and owners shouldn't excuse their dogs just because they are small. However when it comes to other people's judgement a lot is based on perceived risk and how under control the dog appears to be. I have two terriers. Very friendly, but jumpy with it. One in particular likes to jump and lick noses. I don't find it acceptable for them to jump in guests and especially children. We manage it by keeping them on the lead, stair gates in house until they are calm and of course teaching them to stay on the floor. If one of my strategies fails, a child gets a lick on the nose and potentially a fright (I'm not saying that is ok, I don't find it acceptable and try very hard to stop it occurring)
My friend has a very large, equally as friendly and boisterous german shepherd. He recently jumped at my seven year old to say a friendly hello, knocked him to the ground, cut his lip and left a very large scratch on his shoulder. My son was terrified. He was on a lead at the time but is so strong my friend was unable to hold him.
The behaviour was the same but the outcome was very different. Scale that up to aggressive behaviour and I can very well understand why people take aggression from large powerful dogs more seriously. The behaviour is just as unacceptable in small dogs but is a much more manageable risk.
On a slightly different note, I recently met with a behaviourist to deal with an issue with one of my dogs and we got on to talking about differences between breeds during play. I explained my youngest would always meet dogs very nicely but would then jump for them, normally their necks and I was concerned she was showing aggression and wanted to deal with it. We stood in the middle of a large dog park and he pointed out several different groups of dogs playing and predicted how they would play based on breed. One group was a spaniel and a large terrier (not sure of breed, was atleast as large as the spaniel). The spaniel was bouncing in front of the terrier tempting him to chase. The terrier would then chase but quickly got bored and left. They repeated this several times, each time the terrier getting bored more quickly. Then, both dogs standing still the terrier jumped on the spaniels neck. Spaniel squealed, both dogs put on leads and left. Behaviourist explained that there was no aggression from the terrier. He was playing terrier style but to a spaniel (and the owners) this was not okay. Spaniels want to be chased, terriers want to chase catch and wrestle. A chase with no rough and tumble is just no fun.
It was fascinating hearing the behaviourist discuss different breeds and their traits. Anti social behaviour isn't acceptable from any dog but I do think there are definite breed traits that need to be considered during training and that can be mis understood and misinterpreted