It's not a matter of clairvoyance, it's a matter of comprehension. That someone "feels" it's something is irrelevant to whether it actually is that something. Coercion requires explicit threat or force. It's a pretty basic concept. Using the OP as the example, since it's actually relevant: If a landlord says, "Have sex with me or get evicted", that would be coercion. If a landlord says, "Pay the rent or get evicted. Alternatively, you can pay with sex", that is not coercion as the threat of eviction is the result of a failure to pay rent, not a failure to take part in sex. And to reiterate what was already stated, actual coerced sex is rape.
“I have never made but one prayer to God, a very short one: ‘O Lord, make my enemies ridiculous.’ And God granted it.” -- Voltaire
"He who awaits much can expect little" -- Gabriel Garcia Marquez
This would only make sense if the landlord were telling people they would be kicked out unless they bribe them with sex... while still paying their rent. The thread is about sex in lieu of rent, because the tenant cannot pay the rent. So they would be homeless regardless.
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How is this much different than say, you failing to pay bill to company X- and company X charging you a pate payment fee. Since that is coercion under your definition, is this theft? Are toll bridges I paid for in tax money theft?
The OP is an unfortunate situation, but is anyone actually being forced? No.