Destroying things sounds perfectly normal, in terms of seeing how differently you can make things look after doing so, and just having fun. As for killing people... Not so much. Most people I've spoken to on the forums thought it would be fun to kill DCs, but ended up waking from their lucid dream and being completely depressed. xD They're not real, but do you really want to stop practicing morality just because you're in a dream? What's so different about killing someone in a dream than waking life? Sure, they're not real, but you're 100% responsible for whatever happens to them.