The immediate subject is still the issue that Paul has told Timothy to instruct the church about: the conduct of servants towards their masters, both unbelieving and believing. Paul had enough experience to know that apostolic teaching was not always received.
There is also a different form of the error which is pointed out here. There are those who do not actually go and teach something contrary, but who chafe under teaching like this, and only grudgingly comply with it. They do not teach otherwise in an open way, but still they do not consent to wholesome words. They are looking for an escape route which avoids having to comply fully with Paul’s teaching. The word ‘consent’ is the Greek for approach near. It implies agreement by drawing near to a thing. But it may be that we shy away from teaching like this. We push this teaching away from us because it runs contrary to our natural inclinations. We may not contradict apostolic teaching; we just shy away from it. ‘No, I'm going to return good for evil. I am going to argue with my employer. I'm not going to review my conduct in these things. I think this is wholly unreasonable. I'm just not going to put it into effect.’ Now that is a reaction that might take place from some believers behaving badly in employment and so on and just not prepared to put things right and face up to them.