Trying to set a dynamic twig variable using craft.request and a craft global
Are you trying to look up the global variable {{ news.pageTitle }} by having the news part be dynamically set from the first segment?

This answer here might help explain. Then try this...

{% set pageTitle = _context[craft.request.getSegment(1)].pageTitle|default("News") %}

I don't think that's the best way to set the displayed page title for your sections, but I believe that's what you're trying to do.

A slightly nicer way would be to also create a page for each section/channel root and have its URL be the same as the base path you use for the entries in those sections. Then you could dynamically look up the page attached to any entry by using this (sorry it's complicated)...

{% set page = craft.enties.url(entry.section.urlFormat|split("{")[0]) %}

That should find the page with the URL that matches the URL of the section entries (up until the first dynamic part). Then you can use the page title, banner, or any other fields you've put on the page.