Maybe we have already discussed it with lawyers BEFORE having a problem.

This is all a huge gray area. There are no hard and fast rules. But there are lawsuits and potential lawsuits. People get sued for improper use of other people's material. We have no intention of having this happen to us. We want to set of an example of how to do things properly without having to be a legal test case.

In general, a clear attempt to give full credit (which you did), providing a link (hence sending the people whose material you are using some traffic) and making a clear effort to just use brief excerpts and urging readers to get more info from the original site all usually placate anyone who might be protective of their material. Quoting material from another site in its entirety WITHOUT FULL PERMISSION and without any link is generally frowned upon on any site I tend to blog on. On the other hand, material from organizations that are trying to get their word out as widely as possible can be quoted more extensively, though I always still provide a link if I can.

Also, I will remind you once more, on any site you post the publisher and editors have final word. Arguing is poor form at best.