Law enforcement can of course do seizures when it's warranted. But in this case they, as I understand, did not try to get logs in regular ways (i.e. just asking for them) and there actually is no logs useful for them. So it sounds like an intimidation move - "keep logs so we could have them or we'd just take everything". Using you analogy, it's like when FBI wanted records from gun store and the owner said he doesn't have them, they would just demolish the whole store and move it to FBI facility in case they could find something hidden in the walls. Clearly looks like scenario of "you better give us what we want and quickly, or it would be a world of pain for you, regardless of your innocence and absence of connection to any crimes".
Case in point: http://news.ycombinator.com/item?id=3865942