When I said chemicals don't affect organics, I was just referring to the nutrients you're giving the plants and not how they affect the microbe population. I'm sure I could have said it in a better way. I'm a big believer in the nutrients in organics by themselves. Microbes are helpful but the natural levels of micronutrients in organics also set them apart from most chemicals.
Strong chemicals can indeed kill microorganisms. There are many aspects of that effect to consider, though. First and foremost, chemical fertilizers are often just concentrated versions of nutrients very similar or the same as those found in organics. Secondly, organic ferts have many substances in them that create a healthy growth environment for microorganisms. With organics, the more fertilizer you give them, the more of this healthy growth environment is provided as well, allowing the same amount of a nutrient as chemicals without killing the microbes. So chemicals kill microbes the same way a person would get sick drinking twenty gallons of water in an hour. It's a substance neccesary for us to live, but high concentrations of anything can kill. Even if there are some chemicals in the soil, the microorganisms should be fine as long as there is enough of the "beneficial environment" created by the organics being used. There are still other factors like how mixing chemical ferts into the soil will kill more bugs than diluting them in water first.
Now let me say that I always reccomend organics when available. Some people can't find organic Potassium locally and in rare situations where online ordering isn't an option, they have to buy chemicals. Doing so, however, doesn't mean they have to scrap the whole organic process. Adding some but not too much Muriate of Potash can supply the K that the plants need for flowering while organic teas provide N, P and all micronutes.