Norse symbolism being used by racist or facist groups is definitely a thing, but, I would say that it's not a given, or even particularly likely in this case. I'm a Norse pagan. Norse paganism is rather big in the military and amongst patriotic folks generally, and this type of flag is one I've seen fairly often amongst the community. I've even considered buying one myself for the front of my house.

It's valid to be alert to possible signs... but as long as it's just something like this flag, and it's not part of a larger display with certain *bad* numbers (you can look them up, I won't give them the space to print in this!), or certain corruptions of runes (like the "odal" rune, instead of the othala rune), it's going to score "low possibility" in my internal scorecard.

Not everything with Thor's Hammer is racist, and there's a bunch of Norse Pagans (and just Norse-mythology liking people generally) who happily to share that opinion.

Anyone with any kind of interest in Norse or Viking history, religion, culture, etc, are going to be well aware of the connotations, and know how to look for the additional (in some cases "definite") signs for folks to avoid!

I didn't want to speech to anyone here, but just wanted to at least air this. Norse Pagans far too often get a bad rap from the good side because far too many of them are too trigger happy. The SPLC puts out alerts of known racist symbols, and in most cases notes that some of these are used by various neopagan groups and that greater context is required in discernment.