I'll try to explain. You've made it clear that the reason for banning glass in this instance is because it is dangerous and has caused harm. This is very general. It is a useful rule to help distinguish between what may be banned and what it would make no sense to ban. However, it can be insufficient on its own to justify banning any particular thing.
To determine something legal status show be a combination of the following factors
1) danger to society
2) danger to user (killing yourself is generally legal these days but its quite common to restrict things that make it easier)
3) benefit to user
4) benefit to society
5) cost to society by banning it
So with glass
1) moderate danger to society, broken glasses on the floor, crime etc
2) same for user
3) incredibly useful in many cases
4) as 3
5) much of the economy is based around glass, if alternatives are available going to cost a lot in money and possibly in fossil fuels
Hence probably a bad idea to have blanket ban glass, but in more restricted areas this can be justified (lots of danger to the user/society in a crowded drunk pub), very limited benefits and not economically unreasonable to use plastic
Everything in 1-5 to up for debate, say whether we are talking about glass,car, or a gun, but notice what I don't include anything that involves 'freedom' that is simple irrelevant