"It's always been like that, get over it" isn't a good argument. We've had a Tory government for most of my life, and if there's evidence of the scales being tipped in their favour, then it should be discussed and debated.
But the argument being made is that Corbyn has exceptionally harshly treated. A study concluding that right wing papers are not very nice to Labour leaders and that the Guardian and Mirror are more balanced is not exactly earth shattering. Newspapers are not objective and are not required to be. People choice their paper to mirror their world view.
It is not a Corbyn issue, it is an issue that all Labour leaders face. Of course some leaders are media competent and are able to generate their own positive stories even in the more hostile end of the press.
But it is the free choice of the people. If the Morning Star reflected more people's views, they would sell more papers and become a more dominant media player.
If people wanted more left wing papers, someone would fill the niche. More right wing papers are sold, because paper buyers like voters who actually vote tend to be an older demographic.
Now there are measures that could be implemented to remedy false stories, but by and large I would want those more for non-politicians. Politicians have a platform to respond to any allegations, they are in less need of protection.
Freedom of choice and market forces have given us the current landscape. Moaning about it may play well with the faithful, but it is a huge turn off for those outside the party that need to be persuaded now.