Wipe the foam from your mouth.
Then think on this: how did your ancestors - also heathens - come to find Christ if Christians were obliged to shun their company?
It's a mosque.
Correct. Have you ever seen a mosque, or this particular mosque?
The mosque in question has a large library, eating facilities, meeting rooms, a lecture hall and other facilities as well as the part that a Christian would describe as a sanctuary, where worship takes place.
Riposte Catholique is painting a picture of a Catholic cardinal shoeless and prostrate on a mat in the sanctuary, crying out to Allah.
I'm going to guess that the actual events of the day do not conform to this fanciful implication.
But, by all means, convict the cardinal without a trial and without any verifiable evidence - I'm sure you believe that this is the "Christian" thing to do.
“Then think on this: how did your ancestors - also heathens - come to find Christ if Christians were obliged to shun their company?”
Simple, we aren’t commanded to not preach to them. We are commanded to shun their sins and false religions, and are not to give aid and comfort to enemies of God.
“Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness? And what concord hath Christ with Belial? or what part hath he that believeth with an infidel? And what agreement hath the temple of God with idols? for ye are the temple of the living God; as God hath said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people. Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you, And will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty.”(2Co 6:14-18).
And again,
“Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son. If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed: For he that biddeth him God speed is partaker of his evil deeds.”
(2Jn 1:9-11)
Praying with false religions certainly violates the spirit of scripture, which will not tolerate any false religion to share a sense of equality with Christ. Islam is a false religion, and we cannot agree with it under any circumstance, or commune with them under any religions context, even in the smallest of things.
Our commandment is simple, Go and preach to all nations, teaching them Jesus. And our example is easily seen in the works of the Apostles, who went around the world crying “Repent!” and urging all to give up their false gods.