MacDonald has not responded to Herald requests for an interview, but in a video supplied to Stuff he said he was bored at the time and wanted to practise his gymnastics.
"A crowd started to form, sort of egging me on ... I was sort of taking it further and further seeing how high I could go, seeing how far I could push the sculpture."
In another video supplied to One News, he said there "wasn't a sign that says don't climb".
Wellington mayor Justin Lester said he supported the police decision to lay charges.
"Look, it was an act of utter stupidity, really. I encourage people to think twice about doing something this silly."
He said Wellingtonians were "rightfully" upset and disgusted with MacDonald's antics.
"I've seen some pretty silly acts in my time ... this was certainly a very negligent act of a public display of bravado which really backfired quite seriously, but he shouldn't have been there in the first place.
"I look forward to the justice system taking its course."
The Len Lye sculpture had been undergoing maintenance following damage caused during the Kaikoura earthquake when the sea water got into it and fried the electrics and was due to be back in action this month.
But the flexible fibreglass structure was bent and broken after being climbed on Monday.
Roger Horrocks, a trustee of the Len Lye Foundation and author of Lye's biography, said it was not the first time the iconic sculpture had been damaged.
The foundation had no uptake when it previously recommended Wellington City Council block access to the sculpture. He hoped it would now reconsider.
"A sculpture like that has to be proofed against idiots - total idiots who want to destroy it.
"People don't seem to understand that if you lean on it or tug it... it hasn't been damaged to the same extent previously. I mean this guy has actually broken it off, but it has been interfered with and damaged."
