I second #1.
The analogy between indecent behaviour and a soggy swampland - does it refer to anything in particular?
Hard rock provides a solid base that can support a heavy load, e.g. a tall edifice. The opposite is the case with soggy swamp land, which makes for a poor foundation: When a tall or large building is erected on it, it may crack or lean, and ultimately collapse. By analogy, a life or career founded in moral principles and decent behavior is thought to have a solid basis allowing it to endure and prosper, while immorality and indecency can lead to a person's downfall.
I don't find it not suited
The imagery used here seems fairly standard. For example, in the bible we find "thou art Peter, and upon this rock I will build my church" and we might refer to someone decent and principled as having a "rock-solid character". Likewise, we speak of the "morass of corruption", and a modern political slogan demands to "drain the swamp" in Washington. The fact that one tends to become dirty when coming into contact with a morass or a swamp may also play into this: The contact with immoral and indecent people provides a negative influence on those that associate with them.