For me personally, seeing the phrase "both sides" used pejoratively is a red flag telling me I don't need to read any further.

When people disagree about something, hearing from both sides is important. Can this ideal of openmindedness be cynically abused by strawmanning one side while steelmanning the other? Yes, but in that case the appropriate response is to criticise the specific ways that one or both sides were misrepresented -- which is also the appropriate response to a piece that only presents one side, and does it badly. Muttering about "both sides" never adds anything to an argument. All it does is signal a deep commitment to remaining entrenched in your current position.

The problem is the assumption that in most debates there are sides to be taken, and that there are 2 of them. It leads to shoddy journalism where "balance" means finding someone to debate another, regardless of the bizarreness of their position.

In the real world there are many perspectives on a given issue, and a lot to be learned by everyone through open discussion. "Both sides" mentality discourages this, and also tends to give too much airtime to extreme views.

This explains the problem with it:

https://en.wikipedia.org/wiki/False_balance

It's fine if you're talking about something where there are a broad spectrum of fairly reasonable policy positions. It's not fine when you have a TV segment that's like "here's Christina, an astrophysicist from Stanford, explaining how we measure the circumference of the earth, and up next we'll have Bob from the flat earth society"