Gov. Scott Walker refused to back down Monday from his proposal to remove collective bargaining rights for most Wisconsin public employees, saying he needed all the concessions he was seeking. Protests popped up around the state over the weekend and into Monday at the homes of state lawmakers, the Capitol, University of Wisconsin campuses and elsewhere. Hundreds of University of Wisconsin-Madison students and their instructors surged into the Capitol over the noon hour Monday, chanting “kill this bill” and “stop the law, stop the hate, don’t Walker legislate.” Peter Rickman, a 28-year-old UW-Madison law student who led the march, poured out hundreds of homemade Valentine cards outside the governor’s office asking Walker not to break their hearts.