You can say it's nonsense it you want but that doesn't make it true. Increasing marginal tax rates most certainly disincentivises working decisions. Make the top rate 90% and see how it goes.
Of course being paid less makes working less attractive. As does a host of other things, but then again I'm not making the argument it doesn't, go back and look at the context of the original post you seem to have taken exception to, which is about how people misunderstand how tax brackets actually work.
An example would be say, if a wage earner is sitting on say 90k, so doing overtime puts them over 90k and thus up a tax bracket, if they are being compensated for their overtime with penalty rates, then they are still taking home more per hour on the portion of wages above 90k than they are for the portion of wages between 37k and 90k, that's simple maths, and it will work across any tax bracket. So to knock back the overtime on the reasoning that the extra tax alone makes it not worthwhile begs the question as to why is it worthwhile to sell your labour for one price for most of the time, but not worthwhile to sell your labour for more than that for some of the time?
Logically I can see only two reasons why this might be the case, one being a lack of understanding about how the tax system works, thus believing that the labour is being sold for less,( which was what my comment goes to ) and the other being that for other reasons, they value that particular time more highly than they do their normal work hours.
Bit of a contradiction. It's either nonsense to you or it isn't.
There's no contradiction at all.
That people would and do make decisions based on poor reasoning, misinformation and or nonsense is hardly a revelation.