For a moment Hawkeye genuinely thinks he's misunderstood. But no, Peter is genuinely arguing that-

"So what- because this guy had a thing for redheads, that makes it your fault? Peter- if a kid gets shot and I can't save them on the operating table, is that my fault? Did I put the kid there? Did I get him shot? Or is it the fault of the brass who started the whole damn thing to begin with?"