If this applied to @potus I might agree with it but applying it to his personal account is rubbish. You could easily extend that same logic to say that any elected official, at any level of government, can't block communications from anyone on their personal accounts.
Trump using his personal account to comment on "work" (i.e. being President) doesn't de facto make it a work account no more than me complaining about my job on my personal email turns it into a work email.