Any thing that either rewards or denies a person something is discrimination, regardless or reason.
Obv. homosexuality or gender are not races, but biological factors.
I would lump racial, gender, etc. into a category called "biological discrimination"
Most people believe that this type of discrimination is wrong. Some don't.
The problem comes when we get into a discussion of rights and liberty.
MIR used the Thomas Jefferson quote "Life, liberty and the pursuit of happiness." This stems from an earlier phrase that originally voiced these three things as rights of the highest order, "unalienable rights" meaning no one can take them away with out just cause ie. you are a criminal. The earlier phrase also listed property instead of happiness, but that is unimportant to what I'm arguing.
The key term in the phrase is pursuit. No person is allowed to use force to impede another persons pursuit of their goal. Denying someone the voluntary exchange of goods or time is not stopping them from pursuing those goods, it is simply not allowing them to force action on the denier, which itself is using force to deny someone their pursuit of voluntary exchange.