Ask if your abstention or principles actually change outcomes. If it actually makes institutions run differently or society behave better. Principles are good, but you need power to actualize them, and in the mad scramble for said power they can hold you down. It's a delicate balance which is why pressure groups and relatively simple, established platforms do well. Easier to keep track of what you want amidst the struggle
 
That which is must be accepted on a practical level. No rule against opportunistically using dumb mechanisms for what you want
 
Impure victory > principled defeat. Make opponent live up to his own standards (in a meaningful way, not as a gotcha)
 
Especially when out of power (and have polarized opposition) and therefore not actually deciding how these things are used, arguing you'd then be obligated under consistency to acquiesce to do something you dislike is rather silly since your opponents will be under no such compunction and these structures were probably already used that way (or there is rather little preventing it from being so based on your ability to co-opt it)