So what’s a Facebook designer to do when critics assail the service as a “disease,” “drug addiction,” and “your desperate ex”?

Remember the responsibility of serving some two billion people around the globe, according to Margaret Gould Stewart, Facebook’s vice president of product design.

Speaking Monday evening at Fortune’s Brainstorm Design conference in Singapore, Stewart outlined how design practice informs the many changes deployed to Facebook’s many software products.

“Because of the nature of the products that we build,” she told interviewer and Fortune Asia editor Clay Chandler, “design is incorporated into everything we do.” From Facebook’s earliest days, designers had a seat at the table. “There’s an expectation that design is a partnership with engineering and product management to drive the vision ahead,” she said, adding that design isn’t a centralized function at the Menlo Park, Calif. company.

Because of the tremendous scale of its customer base, “the interfaces are critical and incredibly sensitive,” Stewart said. Each change therefore has huge impact. “There’s a lot of rigor associated with exploring the possibilities, using all kinds of insights,” she said. It’s all about “trying to bring as much wisdom as we can” to the process.

“Data sometimes gets a bit of a bad rap in a design context,” Stewart said. “If you’re operating at the scale we’re operating at, it would actually be irresponsible” to not use it to inform decisions.

For example, users may want to share different kinds of information based on their market and expectations. Facebook can’t “fork the experience too much” because the service is, in the end, focused on connecting people.

Caution is key. “Quantitative data tells you what you’re doing, but it doesn’t tell you why,” she said. “The data that we have can inform our design decisions, but it’s kind of dangerous to be led around by the nose by the numbers.”

So Facebook’s designers think a lot about their responsibility to their users. The approach is inherently cross-disciplinary, Stewart said: “It is weighty work and it requires a lot of collaboration with experts.”

And what about those privacy missteps and national security struggles? “I think they’re all design challenges,” Stewart said. It requires skepticism, she added. Not every problem requires a technological solution; not everyone present on digital platforms is a good actor.

“You basically bring all of the things happening in the real world—the good, the bad, the ugly—onto these platforms,” Stewart said. It’s impossible to curtail all of those behaviors, she acknowledged, but there’s a need to address many of them.

Is Facebook’s namesake service so well-designed that it’s actually bad for users? Stewart took a more nuanced approach. “This notion of user-friendly or human-centric [design] is really interesting,” she said. “Being emotionally intelligent is not in and of itself good behavior.” It’s merely understanding someone’s mental state and how to respond; positive action isn’t built in. “Design is the same,” she said. “Just because you can get somebody to do something doesn’t mean you should.”

It’s a mantra about which designers must be careful. “Design is this incredibly powerful persuasion tool,” Stewart said. “There is no such thing as neutral design. The moment you make a design decision, you have infused it with values.”

She then added: “It is in our long-term interest to be a sustainable business and do things for people that are valuable to them.”

For more coverage of Fortune’s Brainstorm Design conference, click here.