Since we are on context (and the Sermon on the Mount), I think it would do you well to see how most scholars divide up chapter 7:13-27. It is typically seen as a unit. That means you can't remove the concept of fruit bearing from vv. 13-14. Not to mention that it is still a stated proverbial principle set at the end with a statement on wisdom and foolishness capping the sermon as wisdom literature. I think it is exegetical suicide to remove vv. 13-14 from the entire periscope through v. 27.
Mat.7:15-20 specifically talk about fruit. But the fruit here is not works. It is doctrine. Jesus said: "Beware of the leaven of the Pharisees." He was speaking of the false doctrine. The fruit of the false teachers was the false doctrine, not the "bad" works. Throughout he is speaking of false teaching, and their fruit--false teaching.
Thus, vs.20, "you shall know them by their fruits," means you shall know them by their doctrine. We know Benny Hinn is a false teacher by his false doctrine, not by his works. Likewise, Mother Theresa. Her works were good; her doctrine was evil.
Also, I see you neglected to mention how I refuted your point about these "discipleship" passages only being spoken to disciples. This was the evangelistic message of Jesus. He would often say hard things to people so they would not follow him. Mark 10 and the rich young guy is a great illustration. The call was for the guy to give up everything and follow him. But the context Jesus refers to it as "having treasure in heaven" "entering the reign of God" "nothing is impossible w/ God" and w/ the disciples asking "who can be saved." So clearly following Jesus was the salvation message.
"And Jesus, beholding him, loved him, and said: This one thing thou lackest; Sell all that hast, give to the poor, take up your cross and follow me."
--LS advocates often use this verse, but it has nothing to do with salvation. Is this what you would tell people to do in order to be saved? What was Jesus saying, and why? The rich young ruler had previously answered Jesus "All these things have I done from my youth," when Jesus told him to "Keep the commandments; this do and thou shalt live." The rich man lied. No man can keep the law. Jesus demonstrated he could not keep the law and the rich man's own sinfulness by telling him to leave his riches. He could not. The rich man went away sorrowful for he had much riches. He coveted his riches more than he desired Christ. That was his sin. That is what Christ demonstrated. Then Christ said to his disciples: "How hardly shall a rich man enter into the kingdom of God." The application is covetousness, not salvation. (Read the account in Mark 10)
Luke 14:26-27 ("If anyone comes to me and does not hate his own father and mother and wife and children and brothers and sisters, yes, and even his own life, he cannot be my disciple. Whoever does not bear his own cross and come after me cannot be my disciple.") was prefaced with Luk 14:25 "Now great crowds accompanied him, and he turned and said to them." This was Jesus message of evangelism as he preached the reign of God which must be entered through repentance and faith.
In these passages he is still speaking to his disciples about discipleship. Certainly it will weed out those who are not true disciples and were simply following him out of curiosity. But that doesn't change the facts.
He was speaking to those who were already saved.