This issue, in Western countries, has nothing to do with "equality", but is politically motivated and homosexuals cynically used.
The object is the removal of social conservatism from society, beginning with the undermining of family values and the established Christian Church.

Close family relations are universally banned from marriage, due to their sexual behaviour, which is deemed to be dangerous, unhealthy and socially unacceptable. The health issues could be overcome by close relatives agreeing to be sterilised, yet this piece of equality is never discussed.   The ban is quite rightly in place for social and legal reasons.

Given the horrific MSM health figures, and the practical redefinition of monogamy and traditional marriage......the equality argument just does not stack up.