it is discrimination against taller / longer legged pax to cram them into a seat because it happens to be the airline standard (or to charge more) and too small, in just the same way as it is to try and charge wheelchair pax because they can't walk.
On the spot, I have sympathy for you, as I am not a tall person and I find a 31" seat pitch tight on the odd occasions when I experience it.
The trouble is that most pax are quite selfish and will not pay any extra to provide accomodation that is more comfortable for others.
They then complain when they feel a tall person's knees in their back or when that person wishes to recline their seat or put their legs into the aisle to get a little respite.
If you look at the obese passenger threads, you'll see the saem sentiments.
They fear that obese people may get "something for free", rather than that the person in the next seat will benefit just as much.
IMHO, the minimum seat pitch in economy should be 34", not that this would be great for taller people, but it would make life more bearable.
Sadly other pax do not share this sentiment and as AA found out, will not pay more for seat pitch.
Unless some pressure group is successful in changing opinions, there are limited options for taller people and most of these involve paying a lot more money.