Imagine a store owner standing by his entrance, letting people in one by one without even batting an eye. Then a woman approaches, he likes the look of her. He holds up his hand and says “Hold it! You may not enter unless you have sex with me.”
That doesn’t sound like extortion, sexual coercion and unlawful discrimination to you? Well, it does to any sane judge.
As for evidence: testimonies and/or email trails can produce plenty of evidence, easily.