The WT continues it's obsessive paranoia with anyone who disagrees with them, going to the extreme of applying 1 Tim 6:3, 4 to them.
They do not quote the whole scripture of course (let alone the entire chapter), and in context the writer is saying that slaves should not hate their christian masters, and then says if anyone teaches anything else he is doting (WT--mentally diseased) on sayings, teachings, etc. Some versions say genealogies.
6:1 Let as many servants as are under the yoke count their own masters worthy of all honour, that the name of God and [his] doctrine be not blasphemed.
6:2 And they that have believing masters, let them not despise [them], because they are brethren; but rather do [them] service, because they are faithful and beloved, partakers of the benefit. These things teach and exhort.
6:3 If any man teach otherwise, and consent not to wholesome words, [even] the words of our Lord Jesus Christ, and to the doctrine which is according to godliness;
6:4 He is proud, knowing nothing, but doting about questions and strifes of words, whereof cometh envy, strife, railings, evil surmisings
The context is devotion to doctrine about Jesus, and about not rebelling against christian owners; the WT uses it against those who have left the organization. The rest of the chapter is an extolling of the benefits of simple living, with several well known maxims delivered about money being the root of all evil, etc.
In other words, stay put, don't trash you christian masters and remember, money isn't everything anyway. The writer is interested in the status quo, possibly protecting the economic interests of the rich christian owners.
For the WT to tar apostates with 1 Tim 6:3, 4 is a blatantly out of context application.
They are also alone in rendering 'nowsn' as mentally diseased, though one meaning can be 'diseased'.
The ancient world had no concept of mental illness or mental disease; those with 'issues' were seen to have demons.
Paul DOES call out those who taught other than HIS message; he does not call them mentally diseased but says that God will deal with them.
Hymenaeus and Alexander were among those Paul said had thrust aside their conscience and he handed them over to Satan; what that means we don't know, but what we know is that they were specifically apostate, saying the resurrection had occurred, and had blasphemed per Paul. He does not say that they were mentally diseased; he reserves that for those who didn't want to be slaves anymore.
The WT's use of this expression, as has been noted, is a slur, and is insulting to the mentally ill and to those who no longer agree with the WT leadership.