Yes, they were also attached to its symbolic value when they used it to condemn miscegenation.
Given atheist, muslims, jews or hindus can get married, and so can blacks, browns, reds, yellows and whites (with one another too, which once upon a time was against "the symbolic value of 'marriage' as a Christian institution"), I'm pretty sure civil marriage has nothing to do with "the symbolic value of 'marriage' as a Christian institution".
> and would be completely fine with another civil contract with the same rights but a different name.
Because "separate but equal" had such a good run last time around eh?
> This seems to be somewhat in line with Eich's actions
No it is not:
1. Eich donated $1000 to prop 8. Prop 8's goal was to prevent future homosexual marriages in california and to break up existing ones (since prop 8 was passed specifically because proposition 22 had been struck down and homosexual couples were getting married). It did not propose the introduction of an equivalent contract or amend californian law to effectively introduce one
2. Eich refused to acknowledge such an intent and stonewalled instead behind "me giving to people trying to destroy your marriage does not mean I'm a bigot". Does not sound like "separate but equal" was his intent, as distateful as that would have been
3. "I would prefer an alternative to it therefore I donate to amend the constitution in order to ban it" is not what I would call sane and sensible reasoning