You should regard these broadcasters as national treasures. Compared to most of the dross that passes for news and entertainment on US TV and radio, they are the pinnacle of quality.
Agree w/ you 100% re: dross, which is why I usually no idea whom posters are talking about when they reference some sit-com or "reality show" character or scene; I NEVER watch that dreck. But, there are a lot of good privately produced shows out there, on stations like Animal Planet, NatGeo, Discovery, History, etc. These pay their own way and give PBS good competition, quality and quantity wise. There may have been a reason for publicly supporting "public" broadcasting decades ago, but no longer, and especially in light of its abuse of that privilege - it has no "right" to these funds - to serve its own political purposes.
Religion has nothing to do w/ it, unless one considers the dogmas of the left as received truths, and public broadcasting regularly airs those much more than they do competing political faiths. As for knowing and catering to one's audience, yes, it IS good for business. But, forcing taxpayers to subsidize businesses like public broadcasting is not so good, for it favors one form of the business of broadcasting over others obliged to make it on their own. And, to equate focusing on local matters with "slanting" - whether of the news, opinion, or the now ubiquitous blending of the two - is as ethically wrong as it's inapposite.