"Blitzkrieg" is German for "lightning warfare". It was a term used to describe a particular set of tactics the Germans used in World War 2 involving very rapid advance across enemy territory using tanks and aircraft.
In U.S. English, people sometimes use "blitzkrieg" to refer to any attempt to accomplish some task quickly. Like, "We're planning a blitzkrieg of advertising on the west coast once the new product is released." Note "blitzkrieg" is a noun. English speakers sometimes use "blitz" as either a noun or a verb. I don't know what proper German usage is there.
In general, it's pretty common to use military metaphors in non-military contexts. We talk about "attacking" a problem of any sort, "targeting" specific opponents or competitors, conducting a "campaign", starting a "war on poverty", etc. Whether such language is inappropriate or offensive is a matter of opinion. Most people don't think it is and use it routinely. If you personally find it offensive, the question of what to do about it is a matter of how important the issue is to you, I guess.
(There was a big deal in the U.S. a few years ago where some Democrats criticized Republicans for using such language, claiming that it encouraged political violence, to which some Republicans replied by pointing out examples where Democrats had used the exact same language. Of course that sort of thing goes on in politics all the time.)