This clearly establishes the doctrine that the heathens are...

This clearly establishes the doctrine that the heathens are unclean people and thus water at their hands and food prepared by them is also unclean and should not be touched or consumed by Muslims.

’In-nal-laaha yah-kumu baynahum fii maa hum fiihi yakhtalifuun. ’In-nal-laaha laa yahdii man huwa kaazibun Kaf-faar. 3. Is it not to God alone that all sincere faith is due?

And yet, they who take for their protectors aught beside Him (are wont to say), “We worship them for no other reason than that they bring us nearer to God” Behold, God will judge between (on Resurrection Day) with regard to all wherein they differ (from the truth): for, verily, God does not grace with His guidance anyone who is bent on lying (to himself and is) stubbornly ingrate!

Whatever good deeds they may do will be so completely outweighed by the sin of being an unbeliever that they will amount to nothing on the Day of Judgement.