From the top down (i.e. should it be allowed to be legal?) its pretty easy to make some arguments against it. But theres also the opposite view i.e. if its not already banned, what real reason is there to ban it? You could make a "guns dont kill people, people do" kind of argument for Monero as well "the currency doesn't spend itself" basically.

Personally I have no idea and I expect to see a high profile court case about it in the next 5 years.