The original sentence:
(1) Some people think that smoking should be banned.
does not carry quite the same meaning as
(1A) it is suggested that smoking should be banned.
or
(1A) it is argued that smoking should be banned.
nor do (1A) and (1B) gave the same meaning. As this comment points out, 1A means just that someone has offered the idea, while 1B means that someone has offered a justification of the idea. Beyond that, (1A) and (1B) are both in the present tense, which should mean that the suggestion or argument comes along with the statement, or has just been made. If the intended meaning is that the idea is generally out there, it might be better to sue "has been. Specifically:
- (1C) It has been suggested that smoking should be banned.
- (1D) It has been argued that smoking should be banned.
But why would one want to rephrase (1)? None of (1A) through (1D) seem improvements to me. (!A) does not say who thinks this, but it makes that clear. The others hide that by the use of the passive voice. The passive voice is not always poor writing, but this seems to me the kind of use that gained it a poor reputation.
Also, (1) indicates that some people have an opinion, it could be reporting the results of a poll. (1A) through (1D) are discussing proposals put forward, not just thoughts.
As to the second example:
(2A) It is sometimes suggested that parents should teach their children about the importance of recycling, while others believe recycling should be taught in schools.
is reasonably clear in my view, but I don't see it as an improvement on
(2) Some people think that parents should teach their children about the importance of recycling. Others believe recycling should be taught in schools.
Why would you think it should be rephrased in this way?