By Caroline Valetkevitch NEW YORK (Reuters) – Stocks on global indexes were sharply lower on Thursday and Treasury yields slid after U.S. data showed consumer spending rose less than expected in May while price pressures were still strong enough to leave the Federal Reserve on its aggressive policy-tightening path. The U.S. benchmark S&P 500 was set to register its worst first six months since 1970, while MSCI’s gauge of stocks across the globe was set for its worst first half of a year on record. The Commerce Department report on Thursday showed U.S. consumer spending rose less than expected …