[formerly_proven]

It's not uncontroversial at all that microwaving people leads to health problems (the article seems to act like that's a contested idea, it is not). The US also has microwave weapons, not secret at all, even approved for use on humans and apparently also used in the US prison system (did they get the paperwork for use on animals?).

Obviously, any CW-capable transmitter may be used for microwaving things, as long as it is sufficiently robust and outputs enough power somewhere in the GHz-range (preferentially). Within that range, anything works really. Penetration goes way down as you increase frequency, but that doesn't have to be a problem. The US Active Denial System uses 95 GHz radiation (at up to 100 kW) to selectively burn the upper 0.3 mm of skin, because this tends to discourage folks from sticking around, for example. This is also why microwaves are 2.4 GHz (besides this being an ISM band), it gives you just the right penetration depth to be quite useful at evenly cooking stuff.