My hunch is that these businesses have already taken their cases to court/arbitration and lost. Otherwise, they would have placed mechanic liens against Trump properties and obtained payment. The argument that is okay because Democrats do it is not a good one; two wrongs do not make a right, and this definitely will not persuade wavering voters to support Trump. The correct argument to use is the above stated.
However, if you want to go down that road (that Democrats do this too) with your wavering voter, I suggest you bring up Whitewater and how the Clintons treated people who missed just one payment on the property they were purchasing!
Many times contractors do crap work and then want to be paid for it. It happens all the time.