Military police considered using controversial heat ray against D.C. protesters

Literally true, but that isn't very charitable to the point they were making.

Window could be open.

The term is "less lethal", not "less than lethal". Meaning they kill fewer people per use, not that they never kill people.

I'm not sure how these particular devices work, "microwave" is anything from a meter to a millimeter which is a pretty broad range (300 MHz to 300 GHz.) Certainly some lengths of microwaves go through glass though, otherwise microwave ovens wouldn't have that metal mesh behind the glass window.

Also I know that microwave ovens normally don't heat glass, which suggests to me they're either very reflective or very transparent to microwaves in the low GHz range. I've cooked enough food in glassware to think it must be the later. (Interestingly if you heat a small portion of glass to red hot with a torch before microwaving it, you can melt the entire piece of glass as the oven heats and spreads the hot spot.)

To the best of my knowledge, that claim is not accurate. Police are issued hollow points because over-penetration is a much bigger concern in an urban, civilian area. In a military context, over-penetration is less of a concern, FMJ ammo is much cheaper, and the 1899 Hague Convention (which the US did not actually sign, but most other major powers did) technically forbid it. Special forces have been using hollow points for a while though, and they were adopted for general use by the US Army in 2015 along with the new M17 (Sig Sauer P320) sidearm.

The ‘Laws of War’ serve different purposes than the law of policing. Feigning outrage that soldiers are prohibited from something police are not, or vice versa, is silly.

Some — but not all — of the differences arise from a general principle that the use of weapons in war is to remove enemy soldiers from the battlefield. A wounded enemy soldier requires far more enemy resources than a dead enemy soldier.

Police are different. If they are going to shoot it should be in circumstances where there is an immediate threat to their own (or another’s) life. The threat should be so imminent and deadly that multiple shots without consideration of whether the perp will likely die or merely be injured is the rule. Stated differently, if a cop has the time and presence of mind to ‘shoot at a leg’, he shouldn’t be taking the shot in the first place.