The 6 or so people I know who have seen the original Numberphile video responded with statements like "I'll never understand math", "that's just stupid", and "I don't get it". None expressed a greater interest in maths as a result; quite the opposite.
Just like a good host at a party, a good educational video should leave the viewer felling positive and better about themselves. So clearly, in this case, it depends on the audience.
That was my reaction too: "This is clearly stupid". The seemingly correct answer to me is that the sum is undefined. Also 1-1+1-1+1-1...!=0.5. That also has to be undefined. I'm not even sure "sum" makes sense as a concept when applied to non-convergent series. But that's just my intuition.
You're right, in the sense that the partial sums are always 0 or 1, so 0.5 away from 0.5.
However the mean of the partial sums converges to 0.5 (this is called Cesàro summation). It converges "on the average" towards 0.5.
However this isn't normally what people mean by convergence.
Interest, with positive or negative context, is interest nonetheless imo. (clarified language to refer to context rather than ambiguous use of "negative")
No. However, unless you have a captive audience you will quickly lose your education opportunity of you don't. Even with a captive audience you are likely to achieve better results if your students enjoy the topic and can feel like they are accomplishing something. Motivation matters as it turns out.
Yes. The purpose of education is to impart knowledge and to instill confidence to wield/apply that knowledge. So if you diminish confidence to "feeling good about oneself", then yes it does.
Just like a good host at a party, a good educational video should leave the viewer felling positive and better about themselves. So clearly, in this case, it depends on the audience.