Speaking on the phone from the South Island, Douglas said he was humbled but did not want to focus too much attention on the remarks.
"I take my hat off to Hayley. He was a very strict, straight up, direct critic. Regardless of that, Hayley made her mark on the world. She's represented New Zealand at a very high level and she has always remembered where her home is," Douglas said.
Westenra responded to the negative review on Twitter, saying: "Every time I come home to Christchurch to do a concert I wake up the next day to a bad review from David Sell. Mr Sell, I get it, you don't like me."
Douglas, who has performed at more than 30 events in the past two years, said the Paradiso tour was the biggest for him by far. "You still get nervous but it's what you do with those nerves that matters - turning those weaknesses into strengths," he said.
"There have definitely been a few ups and downs but I'm a person who just wants to see what happens and wait my turn, rather than self promotion - let life take its course and keep humble."
Douglas is in his third year studying a Bachelor of Music in Performance at the University of Waikato, majoring in voice. He was also selected as a Sir Edmund Hilary Scholar.
Tauranga singing tutor Betty Miller has known Douglas since he was 9 and attended the Hamilton leg of the tour earlier this month. Mrs Miller said Douglas deserved the critical acclaim he has been reaping, including "that review".
"I have supported his career all the way through, from a very young age. I have watched him from a boy singing soprano and helped him with the transition with the soprano voice, so he would have a beautiful deep quality. Now he has a lovely tenor range," Mrs Miller said.