If the mandate had nothing to do with pandemic reasons, why even bother. You know who else used “blackmail?”, Ghandi, that’s the whole point of non violent civil disobedience.
I dunno if I would call causing the very thing you claimed to be protesting against an act of civil disobedience so much as an act of sabotage.
These blockaders are taking away the freedom of other people to move their goods and themselves. That is wrong and the government has laws and tools in place to combat it.