[With the caveat in Imma’s comment]I hold the following combination of beliefs, which are individually relatively common but rarely held together:
Many of the problems that anti-immigrationists claim are caused by migration are real and important.
Nevertheless, the benefits of reducing or eliminating migration restrictions would be so large that it is still a good idea on net.
As a corollary: I have heard many people (the example that springs to mind is Peter Singer in his interview for the 80k podcast, but there have been others) say something along the lines of “I would support open borders, but high immigration leads to the election of right-wing populist nativists who will enact harmful policies, therefore I reluctantly support immigration restrictions.” I contend that it is not the mere presence of people of different ethnic groups that causes right wing populism, but rather the aforementioned problems (e.g. cultural clash, crime, stress on government services, collision with government-imposed inflexibility in the housing and labour markets etc.) combined with left-wing denials that the problems exist (and insistence that anyone complaining about them is a deplorable racist) that drive voters towards the only politicians offering to solve the problems. Therefore, interventions to engage with and reduce the problems caused by migration (“keyhole solutions” in Open Borders lingo) could enable more open borders without a political backlash.