I think the difference lies in the planning. Sure, you can think "wow if I blew this place up it'd really mess things up here", but if you think that and then set out to buy fertilizer and an suv, that's obviously a lot more actionable than a "thought crime".

The law doesn't punish people who have drastic thoughts, it punishes people who have drastic thoughts and then bring them up to associates as something not so drastic.

I dunno, that's the difference to me