In your scenario, you're describing a sportsbook that I simply wouldn't play at, but I don't think Sportsbet sees their decisions as "arbitrary." You see them as arbitrary.

17. Cancellations, Suspensions and Closure
17.1.    Without restricting our ability to rely on other remedies that may be available to us, we may suspend and/or terminate your account, cancel any outstanding bets and/or confiscate any or all funds in your account at our absolute discretion if:
(i) we suspect that you are engaging in money laundering, illegal or other fraudulent activity while using our Website; or
(ii) we suspect that you are depositing funds which have been obtained unlawfully or in a clearly and seriously debase manner; or
(iii) we obtain evidence that you are part of a betting syndicate where several parties are involved in placing bets in order to evade the Sportsbook Rules, these Terms and Conditions or any other rules of Sportsbet.io; or
(iv) we determine that you are using any device, robot, spider, software, routine or other method (or anything in the nature of the foregoing) to interfere or attempt to interfere with the normal proper functioning of our services, any relevant device(s), software, the Website, the casino games, the sportsbook and betting information or any transactions offered on the Website and in particular will not employ or make use of any artificial intelligence or other system (including machines, computers, software or any other automated systems) designed specifically to defeat the Sportsbet.io systems; or
(v) we determine that you are colluding or attempt to collude with other players in order to defraud Sportsbet.io or its customers;
(vi) we determine that you are breaching any term of these Terms and Conditions;
(vii) we determine that you are acting in a manner that is detrimental to the conduct of our business.
17.2.    You acknowledge that Sportsbet.io shall be the final decision-maker as to whether you have violated rules, terms or conditions in a manner that results in suspension or permanent barring from participation in our Websites.