I don't think that a society that allows nazy march can be considered a nazi society as a whole to the point that it deserves to be invaded.

You're conflating a tolerance of Neo Nazi(which translates to demonstrably disrespectful marches of hundreds with blatant impunity in Odessa) with an 8 year war that the neo Nazi russophobic regiment Azov has been waging in Donbass. You think Putin is "invading" because of Nazi wannabes Parading? Putin isn't sending his people to stop parades. He's sending them to deal with the ones who have been waging war for 8 years. Putin isn't there because of parades, he's there because Ukraine broke its word after the second Minsk Agreement was signed and President Zellenzkyy said he won't negotiate with the people in Donbass.