No, they couldn't. sshd usually runs as root* so it can create shells for in user that's logging in. Therefore, only root could kill the daemon. Also, as mentioned by the sibling post, its configuration files are usually(if not you have a serious problem) only writeable by root so nobody else could modify them.

* Note, I guess you could run an sshd that only allows logging in to a single user and runs as that user but both points above still stand even in that case.