It is pretty clear. I would not read genuineness into the fact that they may have had a little American flag, or that they sang the National Anthem.
Liberals (and that is overwhelmingly who many of these people are, or at least who they would be likely to vote for if they gained citizenship) understand intuitively that they cannot show their true face to the American public.
This is precisely why there was so much angst among the Democrats in August, September and October 2002, leading up to the vote that was held three weeks before the midterm elections. The President forced their hand, and put them in a position to: 1.) Reveal their true face to the voters or, 2.) Lie, hold their nose, and say they supported the troops.
Chicken$hits that they are, many of them lied and were fairly transparent about it. I see the same thing with many of these people. Even if they are die-hard La Raza members, they would hold their nose, wave the flag and sing the National Anthem of the USA.
Remember what the principles of the liberals are, as exemplified by the Clinton administration when it came into power, in the opinion of Gary Aldrich in his book "Unlimited Access": Saul D. Alinsky's "Rules for Radicals: A Practical Primer for Realistic Radicals". This book was the handbook for the Clintonistas. It is as foul and despicable a set of guidelines for behavior as there ever was. Boiled down, the ends ALWAYS justify the means. Always.
And this whole issue of ILLEGAL immigrants is just one more example of how they operate.
I'm noticing in all the pictures I'm seeing though they are only showing select sections of the crowd. I haven't seen any wide shots like they usually like to do to show a column of people marching which make the protest look bigger. I suspect it's because they are selecting only the sections in the crowds where they are actually carrying American flags.