Atlantic city’s purchase of a luxury charter bus for senior and youth trips will save money in the long run, Mayor Marty Small Sr. said Friday, calling critics of the $680,000 cost “racists” who are starting their opposition to his reelection campaign next year.“I can’t believe with nonbiased companies like Moody’s and Standard and Poor’s upgrading the city bond rating and continuing to give us a positive outlook, and talk about the budgeting process (as a reason for the upgrade), that on Thanksgiving they are talking about a charter bus,” Small said Friday.