Yes, the fact that you couldn't raze and rebuild Somerville does imply that the existing zoning laws are illegitimate.
Proponents of zoning talk about things like reducing congestion and preserving the character of the neighborhood. If you can't exchange like for like these arguments fall flat. Changing the rules of the game after you've won, so to speak, smacks of crony capitalism. Cynically I believe that zoning laws primarily exist to extend property rights over land that a person is unwilling or unable to buy.
Just to be clear, I didn't mean my comment as a broad defense of zoning laws. Rather, I think it's only fair to consider that there's a very large difference between the relevance of zoning laws when the city is in its infancy and zoning laws when the city is pretty much entirely built up. When the city is, say, 97% built up, any zoning laws should reflect how its residents want the last 3% developed—if at all. I do realize it's more complicated than that (what about redevelopment, for example?), and I realize zoning is fraught with issues and controversy, but I don't think it logically follows that if present zoning laws in an older built-up area don't reflect the existing building stock, that the laws are illegitimate or corrupt. You may not like the zoning laws or the general concept of zoning (I'm not sure I do either, frankly), but that's not the same argument.
Proponents of zoning talk about things like reducing congestion and preserving the character of the neighborhood. If you can't exchange like for like these arguments fall flat. Changing the rules of the game after you've won, so to speak, smacks of crony capitalism. Cynically I believe that zoning laws primarily exist to extend property rights over land that a person is unwilling or unable to buy.