I'm asthmatic and use inhalers which are fine in everyday life, but occasionally when exercising I am wheezing like an old steam train with lungs that feel solid and immovable. My exercise is Audax, twiddling along at 20kph. I suspect that if I was a proper athlete I'd have more issues, so hypothetically it's conceivable that I might need intramuscular steroids to compete on a similar level with non asthmatics.
It's difficult to find a way to balance genuine medical need for drugs that may are necessary for a persons medical condition against use for performace enhancement.
Wiggins worked within the system to obtain his medication, he hasn't broken the rules, we don't know how he was suffering at the time, we have his explanation and his Doctors opinion, his hayfever and asthma could have been bad at the time, not ameliorated with inhalers and to be at his peak performance other treatments may have been required, you can't win the TDF at below your best.
Who knows in Wiggins case?
Maybe the system needs to be improved though.