He's not being punished for using the inhaler. He apparently is being punished for blowing the vapor in the teacher's face.
There are obviously facts missing from this story. Only the student's side is given, and it's given by family members who weren't witnesses, but have an obvious bias.
Ignoring all that, do you want people coming up in your face and blowing asthma medicine, cigarette smoke, bad breath, or anything else at you?