This comical surgery in the first verses is designed to illustrate perspective. No one could have a log in their eye, it is simply a matter of perspective. The standard (log, yard-stick, or sliver -- depending on your perspective) with which you judge is the same that will be used on you. The point is to be humble and care for your own soul, not to ignore your brother.
I love the "How much more. . ." statements about God. This makes it clear to me that I ask far too little of God! I need to change my assumptions and expect Him to be good to me! I wish that was my default, but it often isn't.
It is one thing for the gate to be narrow, but why does the way need to be hard?
The passage about fruit-bearing is one of the most significant warnings in all the Bible. I've noticed in gardening that bad plants don't bear good fruit. Here Jesus says that's true AND that good trees can't bear bad fruit!
How do people prophesy and do miracles in Jesus' name without truly being his. Seems like bad trees bearing good fruit.
Doing Christ's words is the firm foundation, not just knowing them. Knowing them and not doing them is building on sand.