While most issues hold no common ground between humanists and Christian evangelicals, this one could be an exception to that rule. Many humanists and evangelicals agree that felons have the potential for reform, albeit for different reasons.
Here in the USA, we're all used to the downfall of sleazy, ethics-free politicians. But they have all met their match in terms of plumbing the depths of human sludge compared to the loathsome British politician who has just been sentenced to jail for "perverting the course of justice."
Arguments against reasonable, limited gun control are not based on empirical positions but on subjective gut-feelings. The reasons offered to oppose gun control are emotional responses meant to divert the argument from the evidence.