Some of the placards in the protest were unduly personal and did the organisers no credit.
But it was a response to the antagonism rural people are sensing from the rest of the country.
It is true that environmentalists have convinced the great majority of urban dwellers that the country's waterways are seriously polluted and dairy farming is the principal culprit.
Farmers do not deny it but they would like some recognition of the efforts many of them are making.
Dairy farms have agreed to fence off 98 per cent of their land adjoining waterways.
Dairy farmers have come through a tough five years only to find themselves seen as environmental villains.
It has reached the point that some say they are afraid to admit what they do. The environmental campaign against dairying has been so persuasive on opinion that there seems less chance of a sensible trade-off between a valuable national industry and "swimmable" rivers.
Until five years ago a milk powder boom was helping carry our economy out of recession.
A large proportion of sheep farms were converted to dairy units with a high capital investment in modern milking facilities and intensified grazing.
Herds grew to a point that environmentalists may be right that cow numbers need to be reduced.
A water charge such as Labour proposes could reduce dairy farming in regions such as Canterbury where the climate is not suitable.
But in areas such as Waikato the charge would have little impact. Ardern herself pointed out how few of the region's farms use irrigation.
Inadvertently, she also conceded that a charge for irrigation is a highly selective way of making polluters pay for river clean-ups.
Dairy farms in regions of high rainfall are just as capable as irrigated farms of putting nitrates into waterways.
Whatever the stripes of the government that emerges from this election, it is going to need to show greater efforts to clean up the country's rivers.
All farmers - not just those in the dairy industry - have a part to play in helping revive our rural rivers.
And urban dwellers, too, need to recognise they also have an impact on waterways.
No-one should doubt the impact we are all having on rivers and streams.
But farming remains one of this country's essential industries - and as such farmers doing the right thing deserve to remain high in New Zealand's esteem.