Microwave ovens are high powered emitters with wavelengths matched to the ‘resonance’ of water molecules. They are designed to excite and thus heat the water and also the fat/oil in that popcorn bag. Certain military RADARs also can cook/kill tissues. It’s how RF, particularly high powered RF, affects what it penetrates.
Sunlight can burn you thermally and otherwise.
MRI, or magnetic RESONANCE imaging employs lower frequency RF (lower than xray) for form images that is non destructive.
Computed tomography, CAT or PET for example do employ wavelengths that could be harmful if over used. Obviously the ‘harmfulness’ of these wavelengths and wattages can be used for good- like killing tumours.
RF affects what it penetrates.
Let’s say you already knew all that. OK.
Well if you have a modest understanding of RF and biology then it should be easy to infer that a 1/4 watt RF source 15 feet away, with wavelengths 6 orders of magnitude less than Xrays. Is NOT going to hurt you.
I suppose it never occurred to you, that there may be localized bond excitation which have non-ionizing effects but which alter the reactivity of certain species or change the conformation of certain biological chemicals, affecting reaction rates or permeability of membranes to certain species? Or alter the binding sites of enzymes?