[kevao]

By knowingly renting to gay couples is not one complicit in the celebration of a sin?

Is it a sin to show kindness to sinners?

[Steelfish]

Is it a sin to show kindness to sinners?

Yes, if the “kindness” you speak of is to encourage the sin.

John 2:15

“So He made a whip out of cords, and drove all from the temple area, both sheep and cattle; He scattered the coins of the money changers and overturned their tables.”

You wouldn’t call this an act of “kindness”, would you?