If you kicked with the whole FC in mind, you should have the right to change your mind. I guess the only thing I would have done is had a second conversation with them to explain why you changed your mind, before removing them. Tell them why you're dismissing them all together from the FC. This was a personal attack on you as leader. Members of an FC should never talk smack about the head of an FC or it's members in a public forum, and there should be a written rule against this for all to read, which you said there is.
You as leader need to ask yourself "was this an attack on the FC as a whole"? The answer is no, it was a personal attack against the leader of an FC. The fact however is that it was made public by these individuals, when they should have kept it private, rings more wrong than anything else. Airing any dirty laundry in public puts an FC in a bad light. The fact that it hurt your feelings should not have played a role whatsoever in your decision to remove them. Sure they or any member has the potential to repeat this offense in the future hypothetically. You can't really say for certain, nor can you judge them by a hypothetical possibility.
Yet here you are in a public forum talking about all this, trying to defend your decisions, when it's not necessary because it's your rules, your FC. No one is defending bad people but rather expressing different pov's. You can't take everything in here so personal either, but you are. Doing so speaks to people in regards to that initial decision and of course they're going to give rise to it in a forum that you knew was public. By posting here, you basically gave invitation to different views on the matter. You can't ask for people's thoughts and expect everyone to comfort you, telling you you were in the right. It doesn't work that way. You should just stop making this public and personal, it's not good for your FC either.