You really should continue reading to 17a so you don't look so foolish.
"R. Huna said, Israel are holy and do not perform their marital duties in the day-time. Raba said, But in
21 a dark house this is permitted; and a scholar
22 may darken a room with his cloak and perform his marital duty."
So IN A DARK HOUSE this is PERMITTED. Night and day are not the issue. And, of course, the text explains WHY a dark place is required and it has nothing to do with anything you say. But hey...you only see your quote and not Jewish law. That's fine. Cherry picking works for you.
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from another site which explains the text
"(Rava): In a dark house, it is permitted during the day.
1. A Chacham is always permitted. He covers with his garment in order that it will be dark."
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Next question?