why don't you just run in loop something like
for(int i = 0 ;i < blacklist.count;i++)
{
NSMutableString* stars = [NSMutableString alloc]init];
NSRange searchResult = [message rangeOfString:(NSString*)[blackList objectAtIndex:
if (searchResult.location == NSNotFound)
continue;//break or whatever is it in obj-c
for(int j = 0 ; j < (NSString*)[blackList objectAtIndex:i].length;j++)
[stars appendString:@"*"];
message = [message stringByReplacingOccurrencesOfString:(NSString*)[blackList objectAtIndex:i] withString:stars];
}