Nowhere did I suggest that showing "kindness" wins spiritual salvation. To the contrary, Scripture states clearly that salvation is by grace, through faith alone.
And unless I am misunderstanding what you're saying, then you seem to be the one caught up in some kind of pharisaic, salvation-by-works concept.
To return to this renting-to-gays example; if renting to a sinner makes you complicit in his sin, then I surely hope you are not a landlord. If you are a landlord, then most certainly your rooms are vacant. For nobody is sinless, not even the redeemed.
If renting to a homosexual makes you complicit in his homosexuality, then renting to a thief makes you complicit in his theft, and renting to a liar makes you complicit in his lying, etc.
By your reasoning, a landlord could safely rent his room only to the One, Perfect Man who ever lived. But Jesus ain't shopping around for new digs today. He sits at the right hand of the Father Himself, in Paradise.
Or is the issue that you consider homosexuality to be a worse sin than other sins? I can tell you that God does not see it that way. The carnal man would say, Surely murder is a worse sin than lying. But the truth is, if you lived an otherwise *perfect* life, save only one tiny, little, white lie, you are as assured to go to Hell as Hitler with the blood of millions upon his hands.
Sin separates a man from God. One particular sin does not separate a man from God any more or any less than another sin.
You argue thus:
“If renting to a homosexual makes you complicit in his homosexuality, then renting to a thief makes you complicit in his theft, and renting to a liar makes you complicit in his lying, etc.”
Well, this is an inherently false syllogism. Renting to a thief does not make the landlord complicit in the theft, but if the landlord rents the house knowing that his house would be used by the unrepentant thief as a launching pad for a nearby heist the following morning, yes he is complicit. Indeed, in the secular word, this would be seen as a form of aiding and abetting the purported heist.
If knowingly renting to a father and daughter in an incestuous relationship to continue their incest is a sin (and also a crime) why should it be any different to those engaged in acts that are just as abominable to those in a homosexual relationship as do lesbians which is a sin (and was a crime in many states until a liberal supreme Court struck down such laws as unconstitutional) .
I don’t think appeals to “kindness” is of any help here either morally in the secular sense or spiritually in the biblical context.