as already noted, it doesn't say "discrimination". It says "discriminatory practices".

If you wanted to pay people who wear purple scarves less, the first thing you'd need to be able to do is make sure that the purple scarf wearers and non-wearers had no easy way to compare salaries.

That's why this is a step against discrimination: it bans a practice that can be used to discriminate (though it may not be used that way).