I agree that there is a ton of misinformation floating around on the internet. Even legitimate nutritional research is notoriously difficult to conduct well. As you say, almost every diet has its benefits and supporting evidence. You will have people who claim that mostly vegetarian diets are best, and cite the Okinawans. Then you'll have the paleo crowd, who claims that you don't need fruits/vegetables at all and cite the Maasai. I think this comment pretty much sums it up: https://news.ycombinator.com/item?id=14813840.

If I were you, I'd steer clear of any sites that talk about 'toxins', 'detox', 'cleanses', or anything else like that as it's likely to be junk science. Juice cleanses can be particularly hazardous (I am honestly baffled that anybody would think drinking a ton of sugary juice is healthy). I was going to say look for articles that cite their sources, but even the medical literature can be cherry picked to support any hypothesis.

We still have a long way to go before we have nutritional advice that 1. Is actually correct, meaning it's heavily supported by scientific research and has been shown to work and 2. Is accepted mainstream. Until then, I think everyone can at least agree on a few things:

1. Don't eat sugar. Yes, natural alternatives like honey or agave are also sugar.

2. Don't eat refined, processed carbohydrates.

3. Don't eat trans fats.

I think correcting those will eliminate the majority of most peoples diet-related health issues. Everything else pales in comparison.