As a neutral re the McCanns (just parking that in advance), I find the words appropriate for the situation described by the Kate McCann. That is, assuming that the situation was as described in her book, as I have only Kate's book to say that the situation and the expletive existed.
Kate's description about repeated stopping of the tape to explain blood and DNA had been found does not match files or the videos on this point. Keela alerted 3 times. Eddie alerted in lots of places, including lots where Keela did not. The only clear match to Madeleine was in 5A. Therefore I wonder whether artistic licence has been taken by Kate.
The only reference I can find to Kate dropping her head in the interview is in Amaral's book, so I am equally cautious about whether such an event actually happened, or it is artistic licence.
For anyone thinking Kate's expletive might offend the children, here's my take. The files were out before her book, and I would expect someone in her position to mount a strong attack on the dogs, whether that person was innocent or guilty. And Kate would have wanted the twins to know, in the passage of time, that she reacted strongly. Whether she actually did or not, whether the tape-stopping happened as she said it had, or not.