A photographer takes photojournalistic photos of a demonstration showing both sides of an issue. That's what good photojournalists do. Show both sides just like a good writer of journalism.
This is a common misconception about journalism. A journalist's commitment is to the truth, not to "show both sides of the issue". And a journalist's commitment is to tell the story of what is happening in front of him/her — to go in depth into that story, as much is possible, with the information given to him and the one he can find out by research. And his duty is to be fair. Some times the story he has to tell is about one side — the one he happens to be witnessing, the people he happens to be interviewing, the people who are part of the story he's telling — and his/her duty is to tell that story as fairly and truthfully as possible, which may mean trying to figure out if all that is said is truthful or not.
This in no way means telling both sides of the story. Some times a story that has to be told only has one side — you're in a war zone, a school has been bombed, children have been killed. There's not two sides to this. There's just what happened. That's your story. Your duty is to tell it as truthfully as possible. There's a protest in the town of X against pollution of the water supply, same thing. You're first duty is to report on what's happening. To tell that side.
Now it's the duty of both the the media — and the journalists who belong to it — to be balanced. So yes, the "other side" will be asked questions : why was this school bombed? Why has there been no solution regarding the water supply? Sometimes you get an answer, sometimes you don't, sometimes the answer is just bullsh*t. And this you also have to tell or show. Being balanced is not the same as "showing both sides".
Perfect example is climate change. There are no "two sides". There is science, just one side. Same thing with the Earth: it's round, it's been proven round, and you don't need to interview a flat-earther everytime you make a reference to the Earth's roundness.
That said, the world being as complex as it is, sometimes there are three, four, five sides. Sometimes your role as a journalist is to reveal the complexity.
I'll take this one further: there are no sides. Reality is not a coin — one side and its opposite. There are only points of view, there is only perspective.
If journalism was about "telling both sides", it'd be an easy job. It's not. Not today.