Rob, I totally share your concern. However, in this case, they may have had a legitimate reason to investigate, given that it was a 15yo girl that called the police looking for help, while she was pregnant, and AFTER she had already had one baby.
However, unlike the Branch Davidians incident where the police were there to enforce Federal Gun laws (an oxymoron if you ever read the Constitution BTW) the police were there to enforce STATE law regarding the sexual abuse of minors, which is completely within a State's autonomy and proper role, in this case. But, once again, I question the veracity of the State of Texas in this case because "the girl" has never materialized, and her alleged assailant was briefly interviewed by Texas Rangers and permitted to leave without being charged.
What REALLY gives ME pause about this case is what the police are equipped with to confront citizens. I DON'T like the fact that the police COULD take away all of our rights IF they really wanted to. (hint, they could) How? They now employ military hardware to make sure that if they confront a citizen which actually stands his/her ground, that they don't get injured or killed themselves.
I find something VERY WRONG with this picture because it's equipment like this that made the Waco disaster possible.
But I mean, COME ON, what the HELL are they doing employing THIS kind of hardware for CSA law enforcement. Can you say "overkill"?

More can be read about this incident here:
http://freedominourtime.blogspot.com/2008/04/your-children-are-ours.html