I'm thinking more along the lines of a group without extensive conventional warfare capabilities (most non-governmental armed groups) who resort to "terrorizing" civilians in order to achieve their objectives (whatever they might be).
In that case they’ve rendered the distinction between military and civilian moot since they’re not engaging in warfare but terrorism (regardless of whether that’s by choice or perceived necessity). This also excludes that action from the rules of war so we’re not just talking about killing civilians but permitting rape, torture, theft and use of any form of weaponry or tools prohibited in warfare by international law.
If those civilians belong to a democratic country then they share responsibility for whatever crimes the rebel group accuses the government of.
I think it’s debatable how far you can make that connection, even if you’re presuming the democratic system is perfect. Millions of citizens could directly oppose a particular action by their government but if they’re outvoted by a larger majority, there is limited other action they can take. After all, on this basis, if an elected politician is put in prison for breaking the law in office, every citizen in that country would be equally guilty and should be locked up with them.
The answer to your first question is yes (if they belong to a democracy).
You’re basically unconditionally justifying acts of terrorism, by soldiers and unconventional forces alike, against unarmed civilians.
Their support (even of only tacit) may well have led to the deaths of the enemy soldiers and possibly even the enemy soldier's family and friends. Therefore since the civilians support has contributed to the death of others their own life is rightly at risk,
We’re not talking about soldiers now, we’re talking about terrorists. You’re seeking to destroy the distinction between soldiers and civilians on one hand yet using it as justification on the other.