I want to write an essay with this topic: Persuade a reader that science needs to be limited/controlled as it is in the storyline of Brave New World. Use present-day references and references from the book.

Brave New World presents a dystopia where, as in similar books like Zamyatin's We and Orwell's 1984, technology is being used as a means of controlling the population on a mass level. Huxley's vision of the future is different from that of many other dystopian writers, partly because it is described somewhat comically. We might observe that for most of the characters in Brave New World, this dehumanized future, at least on the surface, is actually a lot of fun. Eugenics, the selective breeding done in a systematic way for the entire population, creates a world in which everyone seemingly knows their place. If you are an Alpha, you are presumably happy with that, and if you are an Epsilon, since you don't know any other kind of life, you're supposed to be happy with that as well, at least in theory. The reality, however, is that people like Helmholtz and Bernard are dissatisfied with this sterile, ultra-organized type of existence. Even without the introduction of John, the "Savage," into this high-tech world, we see that something is wrong, at least for some people.
Huxley's implication is that discarding the old values, upon which human life rested in the past, has created a nightmare. People are kept happy and passive largely with the use of drugs--specifically "soma." People have in general become superficial, automaton-like beings. Unlimited science and technology have, in effect, made humans inhuman.
In answering your question, you may wish to look at areas in our twenty-first-century world in which technology has similarly weakened or destroyed those qualities we've generally seen as making us "human." It's a truism that scientific advancement results in a trade-off: something is gained, but something is lost. In many ways Huxley, like Orwell, was prophetic, anticipating developments that would not occur for decades. Were those authors, you might ask, correct in believing that it was inevitable that technological advancement would end up harming, rather than helping, humanity?