Maybe the way you said it offended him. Sometime it's hard to be polite but straight forward. Have to learn from how Ameicans speak. There IS a lot to learn, how to express yourself politically right but to the point.

For example, we just did a project and becuase of the incorrect information the other group gave to us, we had to face a lot of pressure in front of the customers. So here's what my boss communicated to the other group's boss:

There were 2 major pieces of this project and I fell our group was misled on both pieces. To be confident, good people did hard work, sometime with very short notice to complete. But to fix this, our group was under extreme pressure in a very short period of time and had to spend the resources and time we don't have. The good news is, all involved have been helping to get it resolved and now the remedy is in place and our customers are protected.

He told me he could have said the truth: XXX in your group screwed us big time but it won't help in any way. After he said the above, the other group's leader agreed that they made the mistake and the guy who's responsible is very upset and embarrassed.

I think situations like this, are opportunities where we could learn. I wouldn't said it as smoothly as my boss did and the other group's leader didn't feel offended at all.