I don't think I would use the word justified. I would say as someone that's lived in a high crime area that I'm in support of trying to reduce crime rates in areas with high crime rates. I don't think there's anything wrong with trying to reduce the crime. Trump lives in DC. He works and his employees work in the DC area. They want to take action to reduce crime.
I spent some of my life watching people on TV demanding to defund the police and all the other nonsense while they lived in low crime areas and didn't have to suffer from the policies they are promulgating on poor people. I wish trump would do this where I used to live to be honest.
That being said, I would like to mention a basic theory that I have. If you're poor, you're often forced to buy the cheapest options in terms of housing or used cars, etc. When a neighborhood improves and is "cleaned up", property values and rents rise. Suddenly the neighborhood you live in is becomes unaffordable for poor people.
Essentially, there is an economic trap: affordability often comes bundled with low quality, and improving quality often erases affordability when talking about things like used goods or housing. It's not necessarily clear that poor people are the recipient of the benefits of lower crime in inner cities, because without high crime rates, inner cities are prime top tier real estate.
> I don't think there's anything wrong with trying to reduce the crime.
This is the bailey of your motte and bailey argument. The motte is the implication that the National Guard should do this (or rather, shouldn't not do this). Regardless of it being good to try to reduce crime, this is a bad way to try to reduce crime.
Probably not without cooperation from municipal authorities which doesn't appear to be on the table.
There's no federal police force (other than maybe the coast guard and ICE neither of which really have jurisdiction here) so yeah the national guard is the least heavy alternative.
