I'll save everyone a click to this bullshit pseudo-science website and put this archive link (from 2011!) here instead. And since I'm bored, I'll give it quick fact check why not. I may very well also be wrong, so you're all welcome to fact check the sources too!

What may have started as a nutritious plate of food has now evolved into “dead food” due to the dielectric heating of microwaves. “They bounce around the inside of your [microwave] oven and are absorbed by the food you put in it,” writes Dr. Joseph M. Mercola. The water molecules rotate rapidly in the microwave and in the food in high frequencies which creates molecular friction and heats up your food. This causes the molecular structure in your food to change, and as a result diminishes the nutrient content in the food.

Link just goes to Dr. Mercola's homepage website, a pseudo-science website written by someone who is known for dubious scientific claims, not even an article. (Side note, I find it funny that mercola's website URL has been excluded from Wayback Machine)
And are the water molecules bouncing or rotating? The article can't seem to make up its mind about it. And what does it mean by "changing the molecular structure in your food"? Seems like an extremely sensational way to say "the nutrients broke down", which by the way, tends to happen when you cook stuff, microwave or not. In fact, studies show that due to the shorter length of time microwaves need to heat up food, they tend to damage the nutrients the least. Boiling vegetables also robs them of some of their nutritional value because the nutrients leach out into the cooking water.

Microwaves Destroy Breast Milk And Vitamin B-12

If you're going to claim microwaving is bad, then at least also say if heating up via other methods would preserve the nutrients. The article and the study it links to does not say. Not dunking on the original study of course, but this is just a textbook way of spinning a study into something that they didn't claim in the first place.

When you head foods that are wrapped in plastic in the microwave, you can create carcinogens in the food. Based on Russian research and German studies, the Russian government issued a warning [...] says Foodbabe.

Yeah no shit. You're eating melted plastic. Same happens if you put plastic on the stove and eat food from it. No links to the research and studies, link to the Russian gov warning is to Mercola, and foodbabe is also a pseudo-science website. And why would anyone claim a study but put a link to another website and not cite the original source is beyond me.

Microwaves Can Change the Makeup of Your Blood: In a Swiss clinical study, researchers found that... The eight participants in the study ate a series of food...

The link to the study is to huffpost, not an actual study paper, and the article has since been removed by them. Looking at the archived webpage, it was written by Mercola again. The claims in the article itself isn't that different to this one, I'd say it's even more entertaining, including terms like Radiolytic Compounds and Biophotons.
It did say that there were 8 participants, but it also said that it was a significant downside that there was ONLY 8 participants, including the researcher himself, and that his methodology did not stand up to the scientific rigors of the field.

Microwaves can produce effects on your body instantly due to the 2.4 GHz radiation

Link to article is broken/taken down, even in internet archive. So let's look up Dr. Magda Havas and her study instead. This article sums it up quite good. Her Ph.D is in botany, not medical nor EE. And an article also pointed flaws in her tests. She did do a follow up research, but I still seriously doubt the credibility of it. Providing statistics of people who are sensitive to EMI by just asking them, and then place a 2.4Ghz source straight on their chest to test their heart rate, doesn't seem like a great way to test their claims.