"When someone is coming in and arguing and [being] rude to us, if they really want it, they get it. They say: other stores sell it, why aren't you selling it to us?"
Mr Singh said the pressure came from regular and "loyal" customers.
"If they were other customers we wouldn't worry so much."
Owner of Puff'n Stuff on Cameron Rd, Mike Lawrence, said he was happy to continue selling synthetic cannabis.
"Because I believe there is a great number of people that are well over the age of 25, that are responsible using the product as is recommended by the guidelines put on packets by some manufacturers.
"I believe I'm still selling it to people who are old enough and have the right to make their own decisions."
The owner of Dairy 264 in Maunganui Rd, who refused to be named, said she was continuing to sell it because she could not afford to lose the money she paid for the stock and if she did not sell it someone else would.
"We are not doing anything wrong as it isn't illegal, and always ask for identification, and never sell to anyone who is underage. We mainly sell to mature people ... and would never sell it to anyone who can't control themselves or who is acting suspiciously," she said.
She was not likely to order fresh stock until she saw the results of the Psychoactive Substances Bill in July.
Cameronian Dairy owner Jin Kim said he refused to stock legal highs because he was concerned it would increase his risk of becoming a crime victim.
A female staff member at Papamoa Food Market said the store had removed synthetic cannabis from its shelves last month due to publicity about how harmful it was.
Local Four Square managers said it was a company policy not to sell synthetic cannabis.
Rubal Mehta from Hot Spot Superette in Maunganui Rd said she and her husband removed all legal highs from their shelves when they took over ownership about five years ago.
"We stopped stocking any other legal highs because we know it's no good. We know there's a lot of profit margin in selling it but we're just not that sort of people. We would never want to earn money from selling something which puts other people's lives at risk. It's crazy that other stores are still stocking it, and we're 100 per cent behind a total sales ban."
Fraser Cove's Hot Spot Superette owner Carol Hubert said all legal highs were removed 18 months ago.
"It's a terribly dangerous, harmful drug and we refuse to stock it because it's not only harming the person taking it but also their family and the people trying to help them to get off it."
Colorado Dairy, on Cameron Rd, sold synthetic cannabis but the owner was unavailable for comment.
