I think on some level it might be important for gay people to understand the people whose opinion they are trying to sway and tailor their message accordingly. If I am trying to get buy-in for a change I make at work, and I prepare a presentation about it, I go to some lengths to understand the stakeholders and what would sway their opinion in my favor and try to tailor my message to them. For the accounting group, I focus on the money aspects, for the HR group, I focus on associate involvement and impact, for the operations group I would focus on efficiency and productivity. So it is important that I understand my intended audience and tailor my message accordingly if I wish to accomplish anything. Similarly, not everyone who is opposed to homosexuality has the exact same opinion. Some are against it exclusively due to religion, some may believe it is against nature, others may believe it is damaging to children. Not everyone opposed to it has the exact same set of views.
So in a way it would make someone who is not gay qualified to specify what message should be expressed to address their concerns in particular.
If they are not trying to sway anyone's opinion then what is the point of the whole thing to begin with? I don't feel the need to set up a monogamous heterosexual rally in my town, as I do not feel any need to sway anyone's opinion regarding my monogamous heterosexuality.