I'm seeking recruits for my competitive team. I am not seeking to align my Clan, which has over 200 members, with another. Either you join SfD or you don't.
Being a part of the Clan doesn't necessarily mean you are on the competitive team either; it just means you're a member of the server. Only about 20 of the members are on the team(s) while the other 180~ are casuals and honararies. You can very easily be a member of multiple clans, too. Like myself, I'm a member of about 50 Splatoon discord servers. I'm still team captain of Squids for DAYS though. Being a member of another clan does not change this.
I'd be fine joining your clan too, but only if you used Discord, as I can't be bothered with miiverse 99% of the time.