I have a very similar attitude towards bot accounts. Early on, they were instantly recognizable and took no time to identify and block. Now that I'm doing it for a while, I feel obliged to continue and I've discovered that some bot accounts look semi-legit at first (Twitter's 'uncanny valley') but that dragging their profile image into Google's reverse image search would give them away. Same image, loads of different accounts all almost normal but when viewed as a group they were obvious fakes. Curating your Twitter followers list is just a matter of personal preference, nothing more.
And I'm definitely a 'tweet deleter' after reading this article[0] and agreeing with the premise that Twitter messages aren't that important to preserve. I'd rather deny data miners the ability to better profile me than keep old messages. The article's linked-to Ruby script to archive & delete messages stopped working recently but I found a newer one[1] which works very well. Set it up as a cron job, set the preferred threshold for RTs, favorites and time, and it keeps your feed tidy. If that old message was so great your followers will mark it as such and the script will preserve it. The rest disappear after X days.
[0]http://fusion.net/story/50322/meet-the-tweet-deleters-people...