Doesn't C. Botulinum need an oxygen-free environment to grow? I think the holes in the can thing might be letting off the gas they produce, or allowing dirt and dust (containing bacteria) in that is the issue - not the oxygen.
That why botulinum loves low acid bottled (BWB) food - no air, sits in the pantry at the perfect temperature for a bacteria party.
On the freezing corn and beans:
Its not the actual bacteria that make you sick - its the toxins they produce when they are active - multiplying away that its the problem.
The spores are only active between 3 to 4 celsius and 50-ish celsius.
You are right missy they are not killed by freezing, but are inactive, not toxin producing. (if, like Vicki's link said, they are there in the first place) Defrost and cook without delay - for all foods.
Definately defrosting then re-freezing is not good at all... and yes, people do it and might not get sick, but it certainly increases the likelihood. Inactive spores of any variety of bacteria get the chance to happily multiply and start making toxins, then popped back in the freezer for a sleep again so when they are defrosted again the party just starts again, only bigger this time. Its also why defrosting in the fridge is a good idea, as then it is never sitting around in the temperature danger zone (4 - 70 celsius) - especially with large items where the outside may be fully defrosted and at room temperature and the inside stil frozen.
Also a good point is the danger zone in temp when cooling cooked foods before freezing them. I still remember the motto from my cheffing days - four hours at four degrees no deeper than four inches, then into the freezer. NEVER left to cool at room temp if they were going to be frozen. I've sadly thrown out a giant batch of spag that was meant to go in the freezer and got forgotten about and not found til the next day. Just not worth chancing it.
I freeze basil in ice cube trays (and as pesto) every summer. Actually, now you mention it, need doing now as mine is all going to flower.