its business and some will do what ever and justify it as "its not personal its business". He's been getting your thoughts using your equipment and NOW knows your pricing plans probably alot more than you think. I'd be watching out for this person. Next year you may not have to quit some accounts because He will probably do that for you. He'll use the excuse that you said you were downsizing/dropping less profitable accounts and underbid you on every property that falls into the same price point.
I feel your pain the guy down the road from Me under bid every house within walking distance of us. So I know how you feel, he used Me to get started.