If not being legally allowed to discriminate based on irrelevant information causes your business to suffer, you were doing it wrong in the first place, and I'm quite happy to replace you in the market.
It's not irrelevant. It's protected. If it were irrelevant, no law would be necessary regarding this subject and natural selection would wipe out incapable employers who are "doing it wrong" leaving only those like you in business. But if you're a very smart businessman (apologies if you're a lady) you really shouldn't mix up "irrelevant" and "protected", so either you're very lucky or you're not sincere. If a woman struggles raising five kids and her talents barely provide earnings to decently raise only one, shouldn't you question her ability to plan what she does even when she's outside of her bedroom? That's relevant.
Here in the EU there are contracts which allow for unbelievable discrimination. You can discriminate based on sex, age and marital status. Car insurance is horrendously more expensive for young unmarried males than for middle-aged housewives. Before you jump in to replace our insurance companies in the market, here's the bad news for you: it works. It's called statistics.
Have you heard about a guy called Mohamed Merah? As the Principal of a Jewish (not religious) primary school, how would you feel about being forced by law to hire a quota of Muslims as teachers?