LONDON—A man accused of stabbing a British lawmaker to death during a regular meeting with his constituents told a court Thursday he targeted the politician because he voted for air strikes on Syria. Ali Harbi Ali, 26, is accused of murdering veteran Conservative lawmaker David Amess on Oct. 15 during a routine meeting with voters in a church hall in the town of Leigh-on-Sea in eastern England. Ali, who stabbed Amess repeatedly with a carving knife, denies charges of preparing acts of terrorism and murder. Giving evidence Thursday, Ali said he decided to take action in the UK to help Muslims in Syria because he couldn’t join the ISIS terrorist group. “He voted previously in Parliament, not just him,” he said. “I decided to do it because I felt that if I could kill someone who made decisions to kill Muslims, it could prevent further harm to those Muslims.” Ali, …