A noble/attractive suggestion that is uncomfortable to argue against but is ultimately wasteful

I am looking for a phrase to describe the title.

For example; higher water purity when the purity is sufficiently high. Even with an arbitrarily high purity, it would be uncomfortable to argue that "this amount/percentage of toxic material in the water is fine".

What is the name for such a position?

NB: It is similar to this question about having no effect and this question about being unnecessary, but I want to invoke the 'uncomfortable', 'moral' or 'image' concern as well.

What I have often seen is: allowing the perfect to become the enemy of the good. The basic sentiment means that perfection is unattainable, but good outcomes, in politics, policy, software code, etc. are achievable, and marginal improvement should be desirous in these situations.

Here is a Psychology Today

The author introduces the concept this way:

As long as I can remember, I've been burdened with a desire for perfection in all my creative endeavors. No new sentence can be written until the previous one is just right. No garment painted can be abandoned until its texture seems utterly real, as if touching it wouldn't yield the sensation of oil paint but of velvet, silk, or cotton. But my dogged pursuit of this verisimilitude has often proven itself to be the greatest obstacle to my achieving it.

Additional usage history is provided by Entrepreneur

Where did this idea come from: that "the perfect is the enemy of the good"? We don't know, but similar phrases have been attributed to several philosophers and sages throughout the ages:

Voltaire: “The best is the enemy of the good.”

Confucius: "Better a diamond with a flaw than a pebble without."

Shakespeare: “Striving to better, oft we mar what's well.”

Recently, contemporary positive psychology author Gretchen Rubin again popularized the aphorism in her book, The Happiness Project. And through the years, various business people and thinkers have expressed the idea without the pithy pointedness of Voltaire or Confucius.

It would appear that the law of diminishing returns covers this kind of situation:

A concept in economics that if one factor of production (number of workers, for example) is increased while other factors (machines and workspace, for example) are held constant, the output per unit of the variable factor will eventually diminish.

Although the marginal productivity of the workforce decreases as output increases, diminishing returns do not mean negative returns until (in this example) the number of workers exceeds the available machines or workspace. In everyday experience, this law is expressed as "the gain is not worth the pain." - http://www.businessdictionary.com/definition/law-of-diminishing-returns.html