Heckling and protest is part and parcel of political campaigning. Its an example of voters' freedom of speech, and you would be hard pressed to claim that there is any prospect of any harm to anyone. Most politicians respond to this by ignoring it; the witty ones engage with it and use it to their advantage. The National Party, OTOH, assaults people:
A protester wearing a suit was yanked away by Christchurch Central MP Nicky Wagner after popping up right behind National Party leader Bill English while he was addressing a large crowd of National supporters in Christchurch.
The man, holding up a large placard protesting battery hen farming, approached Mr English as he gave a speech before Ms Wagner quickly intervened.
She grabbed the protestor under his arms and swiftly lifted him up and pulled him away before member of Mr English's security team ushered the man away.
There's video, and its very clear that this was a peaceful act of protest. Wagner responded by grabbing the protestor. That's clearly assault, and she should be prosecuted for it.
Of course, that will never happen - we all know the police serve the powerful, not the law. But when Gerry Brownlee threw a protestor down a flight of stairs years ago, he was privately prosecuted and convicted. If the police won't do their jobs, the same should happen in this case. Those in power should not be above the law.