So, is it normal? Well, there's a lot we consider 'normal' behavior for each developmental age-- that said, we don't let it carry on, right?:) I mean, biting is a normal activity for toddlers, but we don't encourage it. It's normal for nine- year olds to start smarting off, but we do correct them. For me, normal means "it's pretty typical that you will see your child trying/doing these activities/behaviors at this age" and has nothing to do with the social appropriateness of said behaviors and activities.
Do teach your son that we keep our sticks pointed low. I have pretty strict park rules for my son regarding sticks: no sticks in the play structure area, because even pointed down, they are at the perfect eye-level for littler children. He's even been given a couple Time Outs for this. I'm serious about it. It's my job to teach him to be careful for others when its not his first consideration because he's busy, distracted or playing.
Teach your son other things to do with sticks. Boys love to collect them....how about making a 'campfire' (gathering a bunch together in a pile) or a "booby trap" (angling and stacking with the sticks leaned up against other items to 'stop the bad guys'...they can do this for a long time).
No, he should not play where kids are pointing sticks at each other's faces,and it's okay to take your kid out of that sort of play. Who cares if the other moms are 'offended' because they aren't watching their kids? Eyes are not easy to replace and damage to the eye is incredibly painful; even scratches to the cornea can cause severe problems which require surgery.
NO, do not expect anything from other parents. Sad to say, but if someone is allowing their kids to play that way (and it's not on my picnic table) they might have to learn the hard way that perhaps they should step in sooner than later. If my kid isn't involved, and their parent isn't enforcing any rules, I've just learned that it's not my business.
Also, I won't let my son or kids in my care play on the top of picnic tables. Please remember-- this is where other people eat. We don't let our kids walk on tables at home for the same reason and the park actually has places designated for climbing. We need to teach our children to respect public spaces; picnic tables fall into this realm.
The balance for me is when the risks outweigh any possible benefit. We don't want to keep our kids in a bubble-- I let my son play some sort of throw-down wrestling tag with the neighbor boy because I can see that they are having fun and the potential for injury is pretty slight---maybe bonking their heads together-- and I know the other kid pretty well. We do have to take it on a case by case basis-- with a rougher child who was flinging kids around hard or if it was on pavement instead of grass, I'd say no. Take in the whole picture, assess the risk, and do what feels right for you and your family. I know a lot of moms who have different levels of comfort regarding risk--don't let another person's 'oh they're fine' stop you from making your own choice for your kids. I've heard a lot of 'oh they're fine's that have ended in tears and ER visits. Use YOUR good instincts!:)
I should add that while it's not necessarily nice or caring to stay out of it, I've experienced a lot of parents who feel that telling them their child is doing something unsafe is just being a nosy nellie. Certainly, there are parents who are tending to their kids and who don't mind being approached --and I don't mind approaching them. But many other times, I've gotten the stink-eye because the parents didn't really seem to care--they just brought the kids to the park so the adults could hang out 'without' the kids. Choose your moments wisely.