If I have found an error on a competitors blog, should I use this to my advantage?

Question from my Quora library

I personally would send a private note with the documentation on the error. I would be sure to sound friendly and helpful. I would rather build a relationship with the blog owner then try to somehow use it to hurt them.

Blogs do better with collaboration and networking then trying to be a lone ranger. You have the potential to even do a guest article on the subject with them. Offer to do an article about the subject.

I'm sure this isn't the way you would prefer to go, hence jumping to use it to undermine the other blog. I urge you to consider though the following the other blog has and the potential of backlash that may result. Personally my preference is ally rather then foe.