I don't care what the context is, calling a former Senator and Secretary of State who just happens to be a woman unqualified to be president is not a good look. Like, I don't care if you were talking about SuperPACs and Iraq, it echoes some really sexist comments that people make about her.
It's also going too far as an attack on someone who is from what is ostensibly your own political party. I'm getting pretty fed up with Bernie Sanders.
I'd go a step further, the use of term 'unqualified' is such a loaded term, but it underlies salient point of running for president of the united states, no matter who someone is, as long as they meet constitutional requirements to run for office (being over a certain age, not running for 3rd term of presidency, natural born citizen etc.) is as far as I am concerned "Qualified" to be president. You can say "more qualified" based on experience or choices in life, but no one who runs is unqualified. The whole nature of the US presidency is anyone who wants to can run for president and the voting public gets decide if you are qualified enough using electoral majority. This shuts a lot of people out but that doesn't mean they still can't be qualified. Even in the nastiest elements of the 2008, I was firm supporter of Obama, I felt he was far and a way better candidate then Hilary was in that race, especially when her campaign started getting nasty as well, but I never once thought she was unqualified, on the contrary I felt her qualification as far experience was concerned and choices she made her in life made her way more qualified then almost all the other candidates save for maybe Biden, but I didn't vote for the most qualified, I voted for the person I felt at the time met my interests and could lead the party and the country the best, and I would still take that vote.
To say she isn't qualified is not only laughable but underscores the very nature of what it means to run for president, anyone who sets there mind out to it can become a president, it is for the voters to decide who they think should lead them overall, but that candidate can come from anywhere in this country and from many different cultures and upbringings. Yes I believe even Trump meets this even if I think he would be one of the worst candidates out there.