Is Autism an excuse for bad behavior?

Absolutely not! I have a child with autism and when he was younger & had a tantrum, we left the store, restaurant, etc. until he could calm down & return to the activity. Sometimes that meant physically picking him up & removing him from the situation & taking a few hits, but we did what we had to do. Once he was calm, we could address the behavior with him.

Stop staring and offer to help clean up the mess.

I have an autistic stepson. I can tell you first hand that if he has a meltdown, there is absolutely NOTHING I can do. Truthfully, I don't take him anywhere with me alone, because I can't control him when he gets to meltdown stage. We try to head them off when we see them coming, but sometimes they are out of anyone's control. A meltdown is NOT a tantrum, it's like a triple tantrum on steroids and caffeine. They are scary and can be dangerous (to him and others). The mother may not have cleaned up the mess because it would have enraged the child more - that's happened to me as well.

well, yes and no...
when autistic kids start throwing fits like that they can hurt people that try to restrain them (it would take physical restraint to stop them most of the time).
the process of learning different calming techniques is long and tedious. Autistic kids throw fits like that because they get overwhelmed by their surroundings- they experience sensory overload like actual, physical pain and they have to learn how to handle it through therapy. Sometimes they are just going to throw fits though and there isn't much you can do about it in that moment.

If I were you I would be saying a prayer for that mom instead of staring at her. She probably feels bad/embarrassed enough already.

i have a child with autism. I like to keep the peace with everyone it's difficult for everyone to shop in the first place and well it is difficult to shop with a kid with autism, but at least you can remove them from the situation for a little bit and if you have a partner that stays home well I would leave them there with them if you are going to use the excuse for them destroying things at the store. My son is destructive, but I make sure he is close to me holding on to the basket and hands in his pocket at all times and if i really need to i have help me so he thinks he is actually doing something good and not determined to destroy things so another can pick it up. My pet peeve on this story is that they didn't pick the things up after he/she decided to destroy whatever it was. I even hate it when I see people with kids at a restuarant and leave a huge mess for the waitress because they are too lazy to clean it up

No. It's not an excuse. That doesn't mean it's not going to happen, but that's no excuse for bad behavior.

I had to jump back in here. Autism is a spectrum - there are kids that are never potty trained or verbal and there are other kids that never exhibit any sorts of bad behaviors or overt symptoms. My SS is on medication, has a full time aide at school, is in several different types of therapy, and we know how to handle him for the most part. His autism is NOT an excuse for bad behavior, we hold him responsible for his actions, and he can and will behave a good 80% of the time with supervision and consistency. What the OP described sounded like a meltdown, and no matter what you think you know about these, until you've experienced one you can't possibly know how out of control they can really be. It's truly like dealing with a scared wild animal. (Which is why we always have 2 adults with him if we go anywhere - not everyone has that option).

Intervening an autistic child (or atleast my autistic child) can do more damage than good. Scratches, bruises, busted lips, etc. can happen....or worse. Not to mention if you step in with my son it takes even longer for him to calm down. I let it run it's course and then I have him help clean up any mess he makes. A melt down in an autistic child is not "bad" behavior. It means they are overstimulated and it's a part if their disorder. They usually can't control it. So don't stare..the mom usually feels bad enough as it is. Offer a helping hand or a caring smile. Something other than a dirty look...we get those enough as it is.

I wish I could answer that, but I believe they can't control it and if that is the case then what are you as a parent suppose to do...

If your child is acting out and you can't control it, how are you going to pick up everything?