But a more significant and darker reason is liberal bigotry undermining Henry.
To a large sector of the audience — and, more dangerously, a large sector of those in a position to comment publicly and shape opinion — Henry is a racist and a buffoon.
In fact, he is as far from the former as you can imagine. And as for the latter, we need more buffoons as smart as he is.
I spent a year and a bit working with Henry making a radio news show and a couple of months working with him on his autobiography. I know him better than most critics. So I can say without fear of incurring defamation action that he has dreadful taste in just about every area where taste can be exercised and he cannot make coffee.
He also has an inexplicable urge to put Christine Rankin in front of a microphone at any opportunity.
But if you want to judge Henry by his friends you might have noticed that one of the closest was the late Sir Peter Williams, QC.
Williams, I'm sure, had his faults, but snuggling up to racists of low intelligence would not have been one of them.
Henry is one of our finest journalists and someone who refuses to make a dull or stupid TV programme.
Among Henry's other talents, however, is a disturbing ability to elicit the most virulent and unreasonable bigotry from liberals.
Many years ago now he said a couple of dumb things.
Most of us say dumb things more regularly but he said them on television and enabled right-thinking, sanctimonious blowhards to lay in and hound him from the air and continue to remind him of the fact for years to come.
Rather than have another look at what he did when he returned with his hat-trick show across TV, radio and the internet, those commentators continue to massage their own egos by lambasting him for offences which, if they are not historic, are imagined. That's lamentable because it fosters the belief that his show, one of the few things worth watching on free-to-air television, is a failure.
The following is typical of the level of social media commentary: "Hey MediaWorks, I won't watch Paul Henry no matter how many promos you put him in but I might stop watching the news bulletin to avoid them."
You can't criticise someone for their opinions if you don't find out what they are.
The refuse-to-watch-no-matter-what approach is the epitome of the sort of closed mindedness of which his critics accuse Henry.
We need more open minds, like his.