Discrimination is a word whose political redefinition originated in the civil rights movement.
In normal usage, discrimination is synonymous with discernment, but as used in a civil rights context it means **irrational bias **against a person. “Irrational” is the hidden qualifier in the term that distinguishes appropriate discernment from prejudice.
In an enlightened society there can be no rational basis for discrimination on criteria such as race, skin color or ethnicity. However, the introduction of morally significant criteria changes the analysis of discrimination.
I share your irritation at the muddying of the notion of “discrimination”. Clearly we discriminate on all manner of subjects on a regular basis and that is perfectly proper.
The law seeks to establish that some forms or bases of discrimination are or should be “universally” unacceptable. In so doing, it seeks to identify and/or promote what ought to be universally acceptable societal norms, eg: people come in two sexes, people have a variety of skin colours, a variety of (bona fide) religious beliefs, etc. and society (through the law) is making the statement: “this is routine, nothing to see here”.
Now as far as I’m concerned, there’s no problem in extending that list to “sexual orientation” - I accept (absent evidence to the contrary) that the orientation simply “is” (however it arises) and does not itself constitute a chosen behaviour. Hence, IMHO, it would always be unacceptable to decline to sell a car to a man because he is a black man, an Asian, or has a same sex orientation. The problem is that the State creates the potential for great ambiguity when it adds some
behaviours to the “acceptable norms” list, and then discovers those behaviours are in conflict with other “rights” and other freedoms people thought they enjoyed. That’s where the “participation in SSM” issue comes in.
At the end of the day, “democracy”, not “theocracy” will determine the societal rules. And given everyone has rights, and these rights may come into conflict, everyone should get to voice their position. The criticism of some religiously inclined persons that they are seeking to live under a theocracy and thus compel others to live under their system of morality is really an attempt (perhaps unrecognised) to suppress democracy, and fails to recognise that the other side of the debate seeks to do the same thing - to establish their cherished rights as (1) universally acceptable, and (2) more important.
Note that these remarks are directed at the debate concerning the right (or not) to decline to participate in activities such as SSM. The question of whether SSM ought be an option under the law is a somewhat different question IMHO.