@Tycho the wanderer: I thought this was one place you could come to ask valid questions without being reprimanded. It is not like this question was spam or anything like that.
I wasn't saying that the question was spam or anything, just that it would be quicker and easier if he were to check the fallout wiki. I'm sorry if I came off as angry, there have just been a lot questions posted that are more easily answered by the vault or the internet.
So I am a nut. That's okay.
And I did look around for awhile for the answer before asking people who would know here. Looks like I was wasting my time typiing in "Fallout 3 Dogmeat good boy" and "Fallout 3 Dogmeat bad dog" kind of stuff, when I should've just used the magic word "dialogue".
Try searching for the Fallout wiki instead, it is called "The Vault"
To find the answer to your question type in "Dogmeat" to the wiki's search box and then read through the article about fallout 3's dogmeat. I believe the answer to your original question is somewhere in that article. The wiki can be very helpful for answering questions about NPCs, weapon locations, quest help etc. That's not to say that you can't come here for these questions, but the wiki may be faster and more detailed in it's description of things such as quest walkthroughs or the location of a rare item.