The marginal tax rate for the rich is 35% and, according to the WSJ, they pay an effective tax rate of 24.6%. If ALL deductions are eliminated and the top marginal tax rate for the rich was lowered from 35% to 24.6%, then the change would be revenue neutral. Moreover the rich can rid themselves of the bills from attorneys and accountants to shelter income, and thereby they would come out ahead.
Look the purpose of taxes is to raise revenue for government operations; deductions are used for social engineering and to accumulate power in Washington. Both of these uses are illegitimate and should be eliminated.
Eliminating deductions is good policy and that's what Republicans should stand for.