Not exactly. It really depends on what you mean by forms of government. If you mean the difference between a Monarchy, a Republic and a Democracy, yes. I would agree with you. But if you mean the Constitution of a government in general, no. There can be immoral Constitutions because they are unefficient in providing benefit to the general population. For me, the main issue here is one of efficiency. Which is the most efficient of the forms od government?
When I look at Monarchies around the world I notice something interesting: they are all very different from one another. That intrigued me over time and I atarted to wonder why. Why is Saudi Arabia's Monarchy so welfare oriented and so brutal, while Liechtenstein's Monarchy is so Libertarian and freeimg. I also wondered why the Early Modern Monarchies were so different from present Monarchies and I came to one probable conclusion: Monarchies are highly modular. Monarchies consist of one person directing the foci of power. It is in this person's best interest to work in a way that guarentees him the maximum amount of support possible. In Saudi Arabia, people are very barbaric and savage, also very religious and in favor of welfare (or else why would they be so fan of Europe?). Thus it is understandable that its Monarchy aims to reflect these values. If you look at the whole of the Middle East it is a barbarous place in general, but the Monarchies seen to be much more stable (they weathered admirably the Arab "Spring", for example, that sprung other middle eastern countries into chaos). In Thailand the military is VERY strong and the Monarch to maintain power tends to need to have the Military on their side. Thus it is common for the King to support coup d'etats in his very country (although he has stopped some). In Meiji Era Japan, the West was gobbling up colonies left and right, taking hold of every opportunity coming from the weakness of its neighbors. Japan's policy then became Expansionism and modernization, which made sense since they wanted to survive. No matter how one might rue Japan's belligerency at the time, one cannot say it was irrational or against its national interests. When one looks at Denmark (a country where the Monarch actually has theoretically semi-absolute power), you see that the Monarch hardly exercises said power and permits the country to work as a Democracy, because if they DID try to exercise their power it would bring forth a constitutional crisis that would dethrone them (Denmark being very much a Democratically minded country). It is interesting how modular the system is and how sensitive it is to the will of the People. Something I do not see personally in equal measure in Republics.