I don't know how the procedure for banning a europarty looks but in Germany the bar is very high. It must be against the core constitutional values (human dignity, freedom, democracy) and pose a threat to that (infamously NPD was not banned as it was found to small to pose a threat).

The procedure here seems to be similar to Germany that the parliament can only request a review from an independent body (in Germany the constitutional court) if this is the case, the actual decision comes from that body after a lengthy process.

Behind the europarty is (among others) the AfD for which the public has been debating for years now on wether to attempt to ban them because of their danger, so it doesn't seem very far fetched for their EU party really.

In Germany it is illegal to have Nazi-like values, such as wanting to expel all non-German people.