Why would African Americans be concerned about the United States allowing thousands of Filipinos to become a part of the United States?

Black Americans occupied the lower rungs of the socioeconomic ladder following the end of slavery—and many still do so today. Immigrants tend to come from lower socioeconomic levels in their home country, but this is certainly not always the case. When immigrants go to any country, whether the US or anywhere else, they often have to take tough jobs in order to survive. This is due to several reasons, including a lack of a family to support them, the lack of a social network, as well as the lack of a social safety net in case they run into financial trouble. Historically, immigrants, whether they are from Europe, Asia, or Africa, are often known to be hard working because they do not have those things that native-born individuals already have.
As with any immigrant group, Filipinos began to create their own communities and businesses. Many times these were in areas already occupied by minorities, such as black Americans. Growing communities of immigrants can slowly displace groups already in an area, creating friction between the two as the native-born population sees jobs and businesses being dominated by others. But as you can see, this is not necessarily an issue between two specific groups but rather an issue that can develop between any native-born group and immigrant group. 
https://www.migrationpolicy.org/article/filipino-immigrants-united-states