So then please tell me what being gay has to do with technology and computing?
Why is the CEO of apple obliged to talk about sexuality?
If you cannot see there is an agenda then you are just plain ignorant. You don't have to be 'homophobic' to identify this clear agenda.
Apple is just one of a growing number of companies to publicly acknowledge that they support equality.
I wouldn't call it Apple or Tim's "agenda" (def. the underlying intentions or motives of a particular person or group.) to "promote the gay agenda" whatever that even means.
Tim Cook is the CEO of one of the worlds most valuable companies, they make computers and mobile devices and are expanding into others areas as well.
They seem to value social and cultural differences. They work towards making products more environmentally responsible, they use solar power for their data centers, etc, etc...
These are responsible acts that better our world, not an underlying motive.
So officially acknowledging he is gay, is not promoting an agenda, it is simply letting people know that regardless of your sexual orientation you can accomplish big things in life if you strive to do so.
The Point:
He is human, regardless of his job/title he has the right to express his opinions. It does't have to be only about Apple products.
Rant:
I see this the same as people who don't agree with actors expressing their opinions on things and say things like "shut up and stick to acting".
They are human too and have the right to express their opinion, you don't have to agree with it.