Two errors are addressed in this passage, one with more vigor than the other.
First, He warns against being sidetracked by empty discussions and arguing about things that don' matter. The solution is to be rooted and grounded in Christ.
Second, He pleads with the readers not to be intimidated by those who keep a rigorous religion. The rigor takes the form of strict adherence to rules or the application of special techniques. They observe certain days, they appear humble, they do all kinds of things and look really, really pious. This is hard to deal with, but the solution is the same as it is for the other error -- focus on the gospel. Learn Christ, who is the fullness of God -- nothing else needs to be added.