Men, on average, are significantly physically stronger than women. Western pop culture — replete with images of 100-pound girls knocking out muscular men twice their size with an artful kick — disguises this biological reality. Indeed, I’ve seen athletic young female college students shocked when an average-sized guy beats them in one second flat in a friendly arm wrestling competition – probably their first direct exposure to the reality of the gender-strength differential. Acknowledging this out loud may get you kicked out of the gender studies departments of Harvard and Boston College, but that doesn’t make it any less true.

Western women often have the luxury of ignoring this biology because of the triumph of classical liberalism, with the supremacy of the rule of law and elevation of reason, decorum, and nonviolence. Of course, violence against women still occurs far too often, including in the developed world. Yet, at least in Western societies, it is understood and accepted that men aren’t supposed to use physical strength to dominate women. If they do, they will be punished – not only with the force of law, but also with public shame.

It wasn’t always this way. It’s taken hundreds, even thousands, of years for our customs and laws to embrace a concept of human rights that holds that the strong should not take advantage of the weak, and that all human beings have dignity and warrant respect.

Not all societies have evolved to this point. Women remain second-class citizens in much of the world, and they are denied basic rights including freedom of movement and the freedom to decide when and whom to marry. Many are all too aware of their physical vulnerabilities and how men can make use of their superior strength. Not only do some societies lack laws against the abuse of women, even where such laws exist, the culture hasn’t accepted the idea that violence against women is out of bounds.

Western women ought to keep this in mind during the ongoing discussion of immigration policy. Many people are uncomfortable discussing the ways in which integrating immigrants from different cultures might impact Western society, and suggest that anyone who dares to raise the question is bigoted against those of different races or religions.

Yet far more is at stake than superficial identity politics.

In fact, most Westerners very much want to welcome those with different backgrounds and encourage a give-and-take between cultures that enriches both newcomers and natives alike. But we must also recognize that not all customs add value to ours. In fact, some represent an incredible, dangerous step backward.

Currently, Germans are struggling with this very notion. On New Year’s Eve, scores of women were attacked near the historic center of Cologne by groups of men they described as of Arab and North African descent. There were more than 90 complaints of robbery and sexual assault, and two rapes. These events took place against the backdrop of Germany’s national discussion about immigration policy, having welcomed more than one million refugees in 2015 into its population of 80 million. German political leaders and the

German press seem reluctant to acknowledge this recent outbreak of violence, and other violent incidences that can be tied to the influx of refugees, which occurred not just in Cologne but in several others cities as well. Yet Germans ought to reject such stonewalling and the completely inadequate response of those like Cologne’s mayor, Henriette Reker, who lectured women to “keep a certain distance that is longer than an arm’s length,” that the city authorities would provide guidelines for young women who find themselves surrounded by aggressive men trying to grope them.

Other authorities have told German women and girls that they need to dress more modestly to discourage incidents. But is the West really ready to return to the notion that a woman should expect to be sexually assaulted unless she fully covers her legs?

Acknowledging cultural difference — and, more frankly, the pernicious, backwards attitudes towards women that exist in much of the world and could soon be imported into the West — needs to be a part of the conversation. One can still support the idea of welcoming refugees, while considering how to balance this aspiration with the need to preserve such core values as women’s equality.

Clearly, scope is a part of the issue. Allowing millions of refugees from one country and culture creates a greater risk that, rather than integration and the adoption of local norms, the newcomers will carry on their traditions, and, in the case of retaining a lack of respect for women, create real harm.

This is an uncomfortable conversation to have. Yet we cannot allow a whitewashed view of multiculturalism to obscure the extent of important cultural differences and the real damage to women’s progress that could result by importing misogynistic attitudes and allowing them to take us backward.