Harangue is a long speech addressed to a large public assembly. Usually the speech is an offensive one (i.e., a verbal attack), but the word can also indicate pompous or tedious speeches.
But what started as a spat at a teenage sleepover swiftly escalated into a three-month harangue of threatening e-mails and defacement of her weblog. (USA Today)
Even as America’s politicians harangue the bankers, the bankers are sniping back. (The Economist)