I'm an spanish citizen thereby granted to have free access to all national territory. If just catalan people is allowed to vote, then they are depriving me, and other spanish citizens, from the right to freely visit/live/work in catalonia.
OK. I will try. I am a EU citizen thereby granted to have free access to all EU territory. If just UK people is allowed to vote, then they are depriving me, and other EU citizens, from the right to freely visit/live/work in UK.
I'm not sure if I follow you. EU citizens have the right to freely access the whole EU territory for work/visit/capital, anything. In fact, that's what the EU is about; freedom to move people or money.
Is not only that. The article 1.2 of the Spanish Constitution clearly states: "The national sovereignty resides in the Spanish people, from whom all the powers of the state emanate."
All Spanish people have the right to decide about all the things in Spain, not just a bunch of people.
Spain is divided by autonomias (comunidades autonomas). You can vote wherever you're registered to vote, nowhere else. I can't vote on issues in Extremadura or Valencia because I'm not registered in there.
I understand this affects Spain as a whole, so after the vote there should be a proper discussion rather than direct secession action (IF that were the result). But this question is regional, the rest of Spain doesn't decide if they want to live in an independent Catalonia state, because they don't live in there.