All religions have their roots in idolatry. They have a wrong understanding of the nature of God and His righteous requirements. When you look closely at their beliefs, it becomes evident they are made up of the fruitless branches of self-righteousness. They think that they can bribe God with their works. Like the Jews of whom Paul spoke -- they go about to establish their own righteousness, being ignorant of the righteousness which is of God (see Romans 10:3). The Law puts the axe to the root. It reveals a perfect righteousness and kills hope of self-salvation. It shows the self-righteous person that the leap he is trying to make to Heaven is infinitely beyond his reach.
I had noticed that Javier had been nodding in agreement at what I was saying. When he asked for my name again, I looked directly at him and said that they could come back any time. We shook hands and we left on good terms. I came away feeling really good because I had avoided doing what the Bible says not to do -- to argue:
"But avoid foolish and ignorant disputes, knowing that they generate strife. And a servant of the Lord must not quarrel but be gentle to all, able to teach, patient, in humility correcting those who are in opposition, if God perhaps will grant them repentance, so that they may know the truth, and that they may come to their senses and escape the snare of the devil, having been taken captive by him to do his will." (2 Timothy 2:23-26)