Hi
. From my limited knowledge I thought Google disapproved of linking to what it classes as an irrelevant page? I guess it's not a problem if it is a human that's being redirected however I also believed that if google saw a redirect which lead to people exiting quickly it meant the value of it got downgraded in google search.
You may be taking this a bit too strictly. As with all things SEO, we should not forget that the site we build are for the satisfaction of our visitors, not Google. So if actual visitors are very often faced with a 404 (because some web site has a link to an article or products you removed for instance), then you should probably do something about it. Your visitors are more important. Also a redirect does not "lead people to exit quickly", not sure what you mean by that. A 404 certainly do, unless you provide valuable information to the user to find another interesting page.
A redirect won't lead Google to downgrade your page. What it will do, if you redirect to an unrelated page, is that you will loose the SEO benefits, ranking signals that the old page may have had. That makes sense, as the page is gone, right? and the new, unrelated page should not inherit the ranking signals of the the old page, because it is, well, unrelated.
Rgds