A bot can easily be exploited, all you need to do is emulate conditions to where it will sell and buy, if you had enough btc you could probably just take their coins in under 5 min, assuming no safeguards were in place like a max BTCn/hr max out.
No, no, no! You can trick a bot with a convex strategy (chasing momentum, for example). You can't trick a bot with a concave strategy (rebalancing, for example).
You are right. We can certainly exploit some bots, because they all have flaws (which are tactical choices) but there is not a "one way for all" in doing this. So a lot of bot on the market would probably have an effect on the market, increasing the activity (whether good or not) and the better bots could take advantage of the weakest. Not in an intended manner, but just because they would be quickest to react etc.