If 99.9% of serious social scientists believe immigration does not increase crime rates, and 0.1% do, then in any situation which tries to be "balanced", like a news program, or a debate, then the people in the minority position become much more known, because it's always the same people.
So you're talking about it not being difficult to find one, out of all the serious social scientists. While I think the comment means that if the serious social scientists are picked at random, then it will be hard to find one that expresses that belief.
As far as I can tell, that's true. Here are some papers I found on the topic, by serious social scientists, who say that immigrants tend to have lower crime rates than citizens, in the US Canada, and Europe:
> "Although a host of reasons exists to expect that immigrants are high-crime prone, the bulk of empirical studies conducted over the past century have found that immigrants are typically underrepresented in criminal statistics. There are some partial exceptions to this finding, but these appear to be linked more to differences in structural conditions across urban areas where immigrants settle rather than to the cultural traditions of the immigrant groups." - https://www.ncjrs.gov/criminal_justice2000/vol_1/02j.pdf
> "it is estimated that the involvement of Hispanic immigrants in crime is less than that of citizens" - http://www.jstor.org/discover/10.2307/3097078?sid=2110551488...
> "First, new immigrants do not have a significant impact on the property crime rate, but with time spent in Canada, a 10% increase in the recent-immigrant share or established-immigrant share decreases the property crime rate by 2% to 3%. Neither underreporting to police nor the dilution of the criminal pool by the addition of law-abiding immigrants can fully explain the size of the estimates. This suggests that immigration has a spillover effect, such as changing neighbourhood characteristics, which reduces crime rates in the long run." - https://ideas.repec.org/p/ubc/clssrn/clsrn_admin-2014-20.htm...
> "Researchers studying the relationship between immigration and crime frequently note the discrepancy between actual rates and public perceptions of criminal behavior by immigrants (Hagan and Palloni 1999; Sampson 2008). A growing body of literature shows that immigrants are less likely to engage in crime than U.S.-born citizens (Butcher and Piehl 1998; Martinez and Lee 2000; Morenoff and Astor 2006; Desmond and Kubrin 2009), and that areas with growing immigrant populations have seen decreases in crime rates (Ousey and Kubrin 2009; Stowell et al. 2009; Wadsworth 2010)." - http://onlinelibrary.wiley.com/doi/10.1111/tsq.12039/full
> Yet, despite evidence to the contrary, public opinion surveys suggest that a large number of Americans believe that continued immigration will lead to higher levels of crime (Kohut et al. 2006).1 This is particularly true when surveys emphasize the (il)legal status of immigrants. For instance, a 2006 Time Poll found that over 70% of respondents were “very concerned” or “somewhat concerned” that “illegal immigrants” “increase the likelihood of terrorism in the U.S.” and “increase the amount of crime,” while a 2006 Fox News/Opinion Dynamics Poll found that 75 percent of respondents were “concerned” that “illegal immigration” could “lead to an increase in crime” (PollingReport.com 2010). - Ibid
> [Europe] There is no simple link between immigration and crime. Most studies find that larger immigrant concentrations in an area have no association with violent crime and, overall, fairly weak effects on property crime. However, immigrant groups that face poor labor market opportunities are more likely to commit property crime. But this is also true of disadvantaged native groups. The policy focus should therefore be on the crime-reducing benefits of improving the functioning of labor markets and workers’ skills, rather than on crime and immigration per se. There is also a case for ensuring that immigrants can legally obtain work in the receiving country, since the evidence shows that such legalization programs tend to reduce criminal activity among the targeted group. - http://wol.iza.org/articles/crime-and-immigration