One of the arguments against gun control is that an armed populace safeguards liberty, prevents the government from becoming tyrannical. Objectively, how effective is it? A tricky thing to measure, the number of violent revolutions prevented.
"Governments should be afraid of their people." (V for Vendetta)
Many liberals fear the tyranny of the upcoming Trump presidency. Should they be arming themselves? Selling guns right now to Muslims and other soon-to-be-oppressed groups seems like a profitable venture.
Fear of the upcoming tyranny may be effective in explaining opposition to gun control to those formerly in favor of it.