The phrase "harmful idea" is correct and usable in written English.
You can use it to describe an idea that may have a potentially detrimental effect. For example, "This economic policy is a potentially harmful idea that could lead to higher unemployment rates."
Ministers reacted quickly with a pledge to ban such a harmful idea by introducing new rules.
There is a well meaning but naive, and potentially very harmful, idea currently doing the rounds in youth justice circles.
The social meaning may finally liberate us from the simplistic and harmful idea, false for many other reasons as well, that each aspect of our being, either physical or behavioral, may be ascribed to the action of a particular gene "for" the trait in question.
"But the basic fact remains, sequestration is a harmful idea.
Society must be protected from the "harmful idea" that "what essentially makes a marriage is romantic-emotional union".
"It mocks and stigmatizes its victims, tearing down self-respect and perpetuating the harmful idea that our unique physical appearances should be compared to air-brushed notions of 'perfect.' What really matters is our character and humanity.
But the insidious effects of stigma and harmful ideas about manhood continue.
However, one of the most notable aspects the whole affair has brought up is just how toxic a locker-room culture can be when it is built upon harmful ideas about masculinity and toughness.
Animated films powerfully, engagingly and invisibly transmit harmful ideas about gender and gender roles.
Meanwhile three faculty members had written the university administration, arguing that Mr. Leonard's project violated the university's research standards in that the students involved were being subjected to something harmful (the idea that there were scientific alternatives to the theory of evolution) without receiving any benefit.
Worst of all, the West infiltrated Byzantium with harmful, individualistic ideas, which destroyed the core values of the empire so the people lost faith in their rulers.Sergei Ivanov, Russia's leading scholar on Byzantium, says all this lumps together a 1,000-year history of Byzantium and crudely extrapolates the result to today's Russia.
