When Hungary, Moldova and Romania give passports to Ukrainians it is not considered an interference in the internal affairs of Ukraine. But when Russia does it, it is considered so. Giving passports to Ukrainians in Hungary and Romania is not seen as an aggression. Giving Russian passports in Donbas is seen as an aggression. The reason is one and very simple. “The West” does not think of Russians as people.
Hungarians and Romanians, as members of the EU are seen as masters in Ukraine, that is why they are allowed to do anything.
Russian decree on enabling the simplified issuing of passports in certain areas of Ukraine's Donetsk and Luhansk regions is considered an attack on Ukraine's sovereignty (see also here for more information).
According to the EU, the timing of such a decision immediately after Ukraine’s Presidential election, which demonstrated Ukraine's strong attachment to democracy and the rule of law, shows Russia’s intention to further destabilise Ukraine and to exacerbate the conflict.