First, this headline from the Honolulu Star Bulletin:
One man's pets is another man's food
There are two things wrong. The first is that pets need a plural verb. It should be One man's pets ARE another man's food. The second problem, of course, is that we shouldn't eat pets. That's a waste of expensive obedience school.
Our friendly pundit found a second error in the story:
Both believe they are trodding the moral high ground.
Trod is the simple past tense of the verb tread (treaded also works). Treading is the form the writer was looking for. (See the story: http://starbulletin.com/2007/07/30/news/story01.html)