So I watched the debate, few points:
-I think bringing up Kissinger can be seen as a valid criticism, because you should always question the kind of people that have influence over any candidate. But I think Sanders is dwelling on the past a bit too much. For instance, bringing up the 2002 Iraq resolution is getting tiresome. That was a long time ago, since then Hillary Clinton has been a competent Secretary of State and also part of the diplomatic negotiations with countries such as Iran.
-People are complaining online that Hillary was pandering to African-American voters when she constantly used Obama as a talking point. I don't think this is necessarily the case. It is not really a secret that Obama prefers Hillary over Sanders; actually most democrats do at this point. All these people (from Obama to Hillary and countless other representatives) want to see a continuation of the current framework. They don't want to risk everything over this concept of political revolution. Most politicians hate the idea of "progressive purity tests", the very reason why the Republican party is a total mess at the moment.
-Sanders is injecting many important issues to this debate, he is giving a voice to all the disenfranchised people. While I personally think Hillary Clinton is the more pragmatic choice at this point, people in Washington have to realize that there is a growing frustration not only in USA but the whole western world. Living costs are getting out of hand while wages are not improving adequately. It is extremely important to defend Obama's legacy but you also need the passion of all these young people if you want to pass any kind of meaningful legislation - be it paid parental leave, student loan and justice reform or equal pay to women. If Sanders loses this primary, as is likely to happen, Clinton really needs to think carefully who she wants as her VP-candidate.
On the other hand, if Bernie Sanders can somehow beat the odds and clinch the nomination, the VP pick absolutely has to be a woman. I'm usually not into identity politics but it is not a good look for the progressive party if the most well known female politician on this planet - who also happens to be extremely competent and experienced - is defeated two times in a row. You have all these progressive political commentators who say that they would "like to see a woman as the president but only if she is the right person for the job and is competent" . Hillary Clinton, on paper, is perhaps the most competent candidate we've seen in ages. If she is not good enough to be the first female president, then I don't know who could ever be....