I guess you didn't read Revere's letter, Rob. The British officers were holding a gun to his head at the time and Revere spilled his guts, albeit inflating the numbers of minutemen who were waiting on them.
Perhaps his intent when he set out was not to warn the Redcoats, but he in fact did warn or inform them (I'm not sure of the reason for quibbling over that word, a warning is not necessarily meant to be helpful), if you take Revere at his word.
"When I got there, out started six officers on horseback and ordered me to dismount. One of them, who appeared to have the command, examined me, where I came from and what my name was. I told him. He asked me if I was an express. I answered in the affirmative. He demanded what time I left Boston. I told him, and added that their troops had catched aground in passing the river, and that there would be five hundred Americans there in a short time, for I had alarmed the country all the way up. He immediately rode towards those who stopped us, when all five of them came down upon a full gallop. One of them, whom I afterwards found to be a Major Mitchel, of the 5th Regiment, clapped his pistol to my head, called me by name and told me he was going to ask me some questions, and if I did not give him true answers, he would blow my brains out. He then asked me similar questions to those above."
- Paul Revere
We were not yet at war, and Revere may have wanted to avoid all out war by warning the Redcoats that we were prepared, while also delaying any Redcoat advance long enough that our side really would be prepared. Sarah's answer was accurate.