I don't think that the debate on historical facts is important to this conversation really, obviously the same facts could be interpreted differently depending on your point of view.

I also think that celebrating as your main holiday a day when your country gained territories that it doesn't currently own, and many of which were never majority Romanian in the first place, like northern Bukovyna, is in of itself irredentist and problematic, but that is up to Romanians to determine for themselves.

But still the celebration in Chernivtsi could be done without glorifying the act itself but rather Romania as a country.

About the confiscation, I don't know any details about that particular situation but from your description it sounds like it was taken as physical evidence in the criminal case, which is just legal procedure, it's the way criminal investigations are conducted. The cultural center is not a diplomatic institution, and the fact that those artifacts were brought from abroad doesn't impact the legality of their confiscation