The south Antrim representative made the comments during the Frank Mitchell's show after loyalists agreed to move a towering structure in the Ballyduff estate over safety fears.
On Wednesday, organisers said they would not make the bonfire any larger, and it would be moved 500m.
Mr Girvan, who was involved in the "eleventh hour" discussions with the community over their concerns, said putting an Irish flag on top of a bonfire to burn it was "part of their culture".
Speaking on radio, he said: "I come from a society that this is part of their culture to have an Eleventh Night bonfire and what goes into that bonfire is important.
"Also some people feel it's perfectly alright to put the flag of a foreign nation, which actually at one time, and let's be honest until relatively recently, was claiming that they had some right over Northern Ireland.
I've no problem about the burning of a tricolour on top of a bonfire, let's be honest. I'm not going to make any apologies for that. That's the flag of a foreign country as far as I'm concerned.
He continued: "There are bonfires in August as well where the Union flag would be burned.
"I'm just saying it does happen on bonfires and on many occasions the people who put it on a bonfire are saying: 'this is something we do not want to see ruling over us'."
Mr Girvan said if burning a flag does cause offence, it should be debated in a proper forum.
In a statement released later on Thursday, the politician said he had "made it clear that the burning of flags can be seen as provocative by those who would hold these symbols dear and I want to see a reduction of this activity".
"This includes when unionist or loyalist flags are placed on republican bonfires," he added.
"We must recognise that Eleventh Night bonfires are an important cultural tradition and if people feel these kind of expressions are under attack it can actually lead to an increase of incidents where flags and other emblems are burned."
Mr Girvan continued: "I will happily work to reduce the incidence of this just as I was happy to help achieve a positive outcome in terms of the location of the bonfire in Ballyduff.
"Hopefully all those who have rushed simply to issue condemnation will be as clear in their support of the right to celebrate the cultural tradition of Eleventh Night bonfires."
I do not encourage anyone to burn flags of any country.
Mr Girvan welcomed the decision to move the Ballyduff bonfire and remove the tyres, adding that the complaints were over the size of the structure, not its existence.
"The young men who are building this live in the community as well, so they see the effect it can have," he added.
"They were not necessarily holding the community to ransom over this. After it was presented in a very coherent and clear form, they were willing to make those movements."
The bonfire was originally built close to houses, and there were suggestions firefighters may have to douse homes with foam in a bid to protect them from flames and sparks.
The DUP man said the decision to remove the Union flag from Belfast City Hall had aggravated loyalists, which in turn led to bigger structures.
"Part of the reason why bonfires are larger this year is because of the flag protests and the decision that was made at Belfast City Hall. That has had a knock-on effect in my community.
"It affects everyone and now we are dealing with the aftermath of that problem," he added.
Alliance leader David Ford has hit out at Mr Girvan for his comments on U105.
The South Antrim MLA said: "It is unacceptable to burn any flag no matter what country it represents.
"As we seek to have a peaceful summer, tensions should be kept to a minimum.
"People are entitled to celebrate their culture, however they should not seek to offend others.
"Politicians have a responsibility to show leadership and set an example. I believe his comments fall well short of what is expected from an MLA."
Meanwhile a DUP spokesman said: "All flags should be respected. We don't want to see anyone's culture disrespected."