The analogy of the right being a fence post and the left being a rabid dog tied to it is not accurate because it suggests that conservative values are immovable, which isn't the case. A more fitting analogy would be that progressives are a rabid dog, and conservatives are a weight slowing the dog down. However, the weight does not stop the dog and, more importantly, moves in the same direction.
For instance, the shift in conservative attitudes toward same-sex marriage in recent years demonstrates that conservative values can and do change. Many conservatives now support or accept same-sex marriage, reflecting broader societal shifts and illustrating that their values are not fixed.