Angela Mason said her appointment marked a new era of inclusiveness in the capital.
Ms Mason, the executive director of gay equality campaign group Stonewall, said the new role was partly symbolic - 'partly Ken trying to make us [gay and lesbian Londoners] feel good'.
She said the 'offensive and redundant' s28 would not inhibit her role as it did not apply to the Greater London Authority.
'At the time of the Government for London Bill we campaigned for, and won, a clause to give the GLA powers to promote equal opportunities.'
Attitudes were no longer as hardened or hysterical as they had been in the past, she said.
'When my appointment was announced in December, The Sun carried a tiny paragraph, but overall there was very little fuss - probably a sign things are moving on.'
Conservative Party assembly members dismissed the appointment as an irrelevance.
Roger Evans, Conservative member for Havering and Redbridge, said: 'This is the latest in a string of appointments to the advisory cabinet. We took the view when it was set up that it was irrelevant and as yet we fail to see anything useful coming out of it. The fact the mayor has appointed a cabinet and makes policy with them is a snub to the assembly.'