All discrimination is morally wrong - discrimination against women, against homosexuals, against animals, etc.

What is important in this world is: “all breathing, existing, living, sentient creatures should not be slain, nor treated with violence, nor abused, nor tormented, nor driven away.”

A person's sexual orientation isn't related to ethics and writing negatively about homosexuality has caused lots of suffering and violence and lots of discrimination and still do.

"Speciesism is wrong because it’s like racism, sexism, heterosexism, etc., which also involve focusing on an irrelevant criterion (race or sex or sexual orientation or whatever) to justify not according equal consideration."

I recommend this article: http://www.abolitionistapproach.com/is-hetereosexism-different/#.UaYwUZxc18E
Please read it and share your thoughts.

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Speciesism is morally objectionable *because* it's like racism, sexism, heterosexism, and other forms of discrimination in that all discrimination involves devaluing the interests of others for morally irrelevant reasons--be the particular reason race, sex, sexual orientation/preference, or species. So to say that you regard using species to devalue the interests of sentient beings as bad but you have no view about the use of race, sex, or sexual orientation/preference to devalue the interests of others makes no sense. In order for your objection to speciesism to be coherent, you must oppose the use of all morally irrelevant criteria to devalue the interests of others.