I don't believe negative advertising should be banned from political ads because I believe there are times when the bad behavior of a candidate should be made public so people can have better informed choices. I just wish that the information could be fact checked before it was allowed to air so they weren't spreading a bunch of misinformation.
Political candidates and committees should make whatever political ads they want to, as long as they don't defame an opponent. It's up to individual citizens to judge for themselves which candidate should win an election. Advertisements can be positive or negative, as long as someone is willing to pay for them. Advertisements are a freedom of expression just like anything else.