You are seeing the “Fraud warning page” because the page you want to visit is listed as dangerous on some blacklists. Opera does not maintain its own phishing, fraud, or malware blacklist. The blacklists are provided by several partners, such as PhishTank and Netcraft for phishing and fraud, and AVG and Yandex for malware.
If you think that the blacklist provider has made a mistake, you can click the “Why was this blocked?” at the bottom of the fraud warning page. link to see which blacklist provider has identified the malware. You can then contact that blacklist provider to inform them of their mistake.