Convicted murderer Michelle Kosilek said in an interview with a local gay and transgender issues magazine that he was disappointed that a notable liberal icon, U.S. Sen. Elizabeth Warren, had voiced opposition to his effort to get a sex change on taxpayers’ dime.In the interview with Boston Spirit, Kosilek, 64, who was born Robert Kosilek, said Warren’s comments that a sex change operation would not be a good use of taxpayer dollars were “disheartening.”