"Editorial bias" and "opinion article" aren't mutually exclusive.

Is there bias in what opinions SciAm chooses to print?

If that was the point the original article was trying to make then they should have provided evidence of that, rather than selecting a couple opinion articles to try to build a case for their own very clear ideological leanings.

There may or may not be editorial bias at SciAm -- no idea since I don't read it, and not really interested either way -- but that article was a shoddy piece.