Those statements were made in different contexts, and so can't really be associated with each other. The point I was making in the "police are not soldiers" comment was that soldiers are expected to kill and die for their government as their primary function. A law enforcement officer's primary function is to maintain public order and enforce local, state, and federal laws. The ability to use lethal force is a secondary function of their role that stems from the simple fact that violent criminals exist that aren't going to take too kindly to be arrested.
The other statement you quoted was made in the context of the discussion about whether or not the state has the right to use lethal force against it's citizens. The main point of that was that governments do maintain that right, and even have the privilege to extend that right to any government agency they deem necessary. Hell, the federal government could put the IRS under arms if they went completely crazy and thought doing so was a good idea.
As Bugfatty already pointed out, Waco was a completely different situation due to the presence of children and unarmed civilians mixed in with the armed suspects. Despite popular belief, the police actually don't like killing people they absolutely don't have to, especially children. The commander on the ground at Waco was probably heavily influenced by that fact and probably spent that entire 2 month siege trying to find a way to end the standoff without bloodshed, but simply couldn't in the end.
In the Dallas scenario, there were no uninvolved civilians or children to worry about so the decision to quickly end the standoff became a lot easier to make.
