I assume you are talking about this site, which is not rated down by competitors, it inherits the poor reputation of its parent domain as explained on the scorecard:
http://www.mywot.com/en/scorecard/romansummi.textcashnetwork.com
You might also be talking about this site, which appears to be blacklisted for phishing and again, not rated down by competitors:
http://www.mywot.com/en/scorecard/dragonsurf.biz
Your suggested method of manipulating reputations simply doesn't work either, work as explained in the FAQ:
http://www.mywot.com/wiki/FAQ#Reputations_are_easy_to_manipulate
Otherwise, you would have probably just rated the sites a few times yourself to change the reputation.
Anyway, should you feel your site has been unfairly rated, follow the "Click here if you own this site" link on the scorecard to claim the site and request reviews on the forum.