I don't think "straw man" quite means what you think it does...
AFAIK it means invalidating someones opinion by taking down the character. Thus that person are not allowed to have an opinion on a matter they are not equal: Only someone with AAAs can comment on someone's AAAs, right?
many people are busy with extracurricular activities during their schools years and they still manage to get excellent grades. Hardly an excuse for poor marks.
No one has made excuses here from what I could tell.
I'm saying that:
A) 8 hours a day for study as you get home at 2pm and going to bed at 10pm. Which was the norm when I was at school.
B) 4 hours a day "open" as you get home from work at 6pm and going to bed at 10pm. That leaves 4 hours in the week, but in that time additional things has to be done such as chores, wife, kids, homework, gym etc.
Without the added benefits of B you have a lot more time which can easily be divided into continuous study and focus, because lets face it in school your sole duty is school and the matter at hand is a lot more simpler.
Your whole basis of your argument rests on the fact that a person are only allowed to say something on the matter if they have same or more As. If we take that person, once they get out of school and mature past college/university they will have to take some of B's responsibilities. This is true for anyone as it doesn't change or being dependent on having As or not; time management will come into play as this is unavoidable.
For the added part of your argument I have not argued that after school you magically develop an inability to get good grades nor have I said that in that his context it is to go without praise. However it should be looked at with a balanced eye and not as something so great without remembering the differences between A and B. For the record I've also attained good marks on all my subjects while being in the position of B although it was not 8 or more concurrent subjects.