Your reaction is overdone.  There's nothing racist in that comment because we don't know who they all are.  To date we know very little about these migrants except perhaps that they were in the US illegally and don't want to go through their refugee process.  I expect they belong to all races.   I'm sure most of them are harmless but some may not be so innocent.   As long as  process is followed, I'm sure we will be OK.