I will give you Parva's comb through of what it takes away.
Roughly, poor people don't pay any federal income taxes (they pay taxes to the federal government based on their incomes, of course, just not what we define as federal income taxes). So when you start taking away goodies (deductions) you are (mostly) hitting the middle class, who probably don't save very much money from these goodies but on the other hand ever little thing still counts for these people as middle class ain't what it used to be, and the upper middle class, who take a larger share of this stuff. So it's always easy to say that taking away deductions is actually PROGRESSIVE because those deductions benefit people who aren't exactly poor. But you have to look at the whole package, not just things in isolation. It's a tax bill which takes away goodies for the middle and upper middle class in order to pay for a massive corporate tax cut and a tax cut for the super rich. For the individual taxes it does this by taking away the AMT and allowing expansion of pass-throughs at a cut rate so no rich person will ever earn a "wage" again (also, too, estate tax repeal). They'll just send a bill from their consulting company.
Parva's list isn't exhaustive. They take away even more goodies.
