The debate isn't really about the £80k earners but about the top 1% of earners which is where the highest impact is for the UK.
The link that was posted earlier showing what your tax bill will be under a labour government is interesting. By Labour's own calculations, at around £661,000, your take home pay is less than half of your gross/headline salary because you will pay an extra £31,000 in tax, so a bit more than a few quid.
Earning £661,000 puts you in the top 0.1% of income tax payers, so we are only talking about 30,000 people out of 31m taxpayers. However, the UK relies on those 30,000 people for 14% of all income tax receipts and a similar proportion of other taxes eg vat.
Research shows that more than half of those 30,000 live in London in a handful of constituencies, and work in the financial services industry. In the same way that Trump has ignored the impact of globalisation and technological advancements on middle America, Corbyn is doing the same ie assuming that all of those 30,000 people will hang around to be taxed more when they mostly work in a global and technology connected world is quite frankly bonkers.
And those that do stay will react to losing half their income to tax. And not in the extreme ways like hiding assets (only about 3,000 in the UK could afford to try and evade taxes) but in more ordinary ways like being less entrepreneurial, working less hard, retiring early, moving abroad and being more focused on tax planning (eg maximising ISA contributions) and doing silly things like investing in film partnerships. Also, it makes it harder for global financial services organisations in the US and Asia to persuade their people to move to the UK so the UK loses out there.
And what's even more odd is that this is all exactly what happened in the 3 years after Labour raised the additional tax rates to 50% in 2010.