If you want to split hairs about exact terminology, then /reasons/casus belli/. I hope we don't disagree that their "denazification" story is bullshit.
In fact there is little to no point in discussing the casus belli part.
Because, in spite of your opinion, its not bullshit.
What would the USA do if Mexico or Canada were suddenly sprouting up clandestine bio-warfare laboratories, funded by Russia or China, within miles of its border? What would Israel do if Iran had funded similar biolabs on its borders with Egypt or Jordan?