Yes, you're right. You can think of "to be + past participle" to be similar to "should be + past participle" in the context you have noted.
However, "should" is a modal verb that implies an obligation/duty, whereas "to be + past participle" is stronger and acts as an imperative in this specific context.
In other words, think of "should be + past participle" as mere advice, and "to be + past participle" as a command.