The sign read: "What a pathetic country this is, which allows two poofters to marry and adopt children legally yet stays with an old religious law that curtails everyone else's freedom of action."
Mr Brown said he painted the "gay okay" slogan to send a message to the community that not everyone shared "such divisive and unhelpful attitudes".
"I felt the sign required some sort of response to say it wasn't okay to put up something as divisive as that sign.
"The owner of the Wanaka Sports Centre really acted irresponsibly and without regard for the real people that live here who were insulted by the use of a derogatory term like 'poofter' and the suggestion that the just acknowledgment of one group's human rights somehow combine with Easter Sunday trading laws to make this a 'pathetic' country."
Mr Brown said many people were proud of living in a tolerant society that allowed everyone to enjoy "freedom of action".
"I wanted to give the message that New Zealand isn't that bad and diverse society is actually a good thing."
Mr Brown said he acted alone in painting the window but had support from others in the community.
"I didn't consult with any other individuals in doing it, but I am generally aware of people around me that felt it was below the belt."
Yesterday shop owner Fiona Crutchley declined to comment.
Mr Brown said the owners were alienating a section of society that might otherwise have sympathised with them in being unable to open on Easter Sunday.
"If they think that they haven't offended any of their own potential customers then they should think again, gay people and their partners fish and play sports, too."
Wanaka police were not pursuing the matter yesterday. Detective Derek Shaw said they had not received any complaints.
"We were not invited to be involved and we are not seeking to be involved."