The phrase "a dumb idea of" is correct and usable in written English.
It can be used when expressing a negative opinion about a particular idea or concept.
Example: "I think that a dumb idea of starting a business without a solid plan could lead to failure."
Alternatives: "a foolish notion of" or "a silly concept of".
In fact, in a digital economy it's a dumb idea to tax sales of any kind.
Another Michigan Republican, Representative Fred Upton, said that the notices "were a dumb idea to begin with" and that members of Congress would now be left to clean up the confusion created by the I.R.S. among their constituents.
Many are terrible throwaway games created by someone with a dumb idea and some knowledge of Flash, but a few are brilliant.
KASEY TAYLOR, NEW YORK This is a weird gift (and, frankly, kind of a dumb idea).
"This is just a dumb idea," said Frank Sanchis, executive director of the Municipal Art Society, a nonprofit group that has influenced city planning and public architecture through most of the century.
While for-pay radio may sound like a dumb idea, anyone who spends a lot of time driving can attest to the frustration of losing the signal of a great station as the drive wears on.
And, also, a thing that Lorne [Michaels] instills in all his writers: Write to the height of your intelligence, even if it's a dumb idea, try to write the smartest version of it.
At any rate, there is your button on the whole "Hillary-Biden switch" story: it was a dumb idea that was mainly the product of idle chatter and breathless gossip, but Bill Daley took it seriously for a hot minute only to discover that doing so netted him nothing more than a pointless expenditure of time and spirit.
This meme is just a good example of how far a dumb idea can travel even when it's a straight-up lie.
