To me it simply says that you should not concern yourself with the defects of others, since it is your own defects that will be the cause of your judgement. When you are busy judging others, you don’t realise that this is the judgement that will be made of you, so concern yourself with your own judgment.
The intent is to knock you off your pedestal.
There are rightful judgments to be made. If you are strong in an area where someone is weak, you have the right and indeed the duty to show that someone the right way to go.
[There are rightful judgments to be made.] But then once having given the advice (whether or not taken) one must take care to keep standing on the Lord, not to pretend that the advice you gave came from oneself and thus get proud.