bugfix to respect `excluded-columns` and prevent SQL errors

There was an error where `excluded-columns` were respected when
building the list of columns to insert, but not respected when
building the list of values to insert. The code was generting insert
statements like:

  INSERT INTO FOO (/* 10 columns /*) VALUES (/* 11 values */)

This patch fixes it.
Specializing on print-objects stream param has unportable effects