Tarmach, I think you will find that an employer can specify any qualifications he wants, as long as they don't discriminate by race, sex or religion. 'Discrimination' by age or qualification is perfectly legal, if there is a good reason for it. Flight safety is a good reason.
Your hypothetical example of a city employer is not a good one; you'll find that they do discriminate by business school and MBA provider. Note that no airline specifies which school you should have gone to, just what qualifications you should have before applying. The fact that only a few schools offer integrated courses isn't the airlines' fault. It would be different if BA (in this case) owned the school(s) concerned.
The bottom line is that in BA's opinion (and experience), the recent graduate from an integrated course is more likely to pass their demanding training than a low-hour modular graduate, hence the insistence on the (still low) hours for modular candidates. You are wasting your time and energy complaining about it; many airlines (including mine) insist on far greater hours and experience before they will offer even the opportunity to apply. This is not a charity for wannabes, it is hard-nosed business. If you want to get in, you jump through the airlines'hoops - and you knew what they were before you started. As I said in an earlier post, do it soon, because it will get much more difficult as the industry starts winding in its recruiting as the slowdown begins to really bite. Don't be surprised to see 1500 hours being asked for - if any recruits are wanted at all - in 6 months to a year's time.
I'm not trying to put you off, but you do need to be realistic about both your task in making yourself employable, and the airlines' right to employ whoever they want.