This is incorrect. The government of Canada does not prevent anyone from having more than one citizenship (like my brother).
If your parents were to become Canadian citizens, the decision to revoke their Dutch citizenship will be solely at the discretion of the Netherlands government.
Same with your wife. It would be the Japanese government that would take away her Japanese nationality.
Neither of your situations have anything to do with the Government of Canada. The only criteria for citizenship, if not born in Canada are that you
- Are a Permanent Resident (PR)
- Declare that you plan to live in Canada after you become a citizen
- Have lived in Canada as a PR for at least 4 years out of the 6 years (1,460 days) before you apply
- Be physically present in Canada for at least 183 days of each year during the 4-year period
- Apply for citizenship from within Canada
Which is why I think PR's should be allowed to vote.
I would hazard a guess that most PR's value their countries Citizenship in addition to their Permanent resident status over the ability to vote.
PS. If you read what I said, I never blamed the Canadian government for their situations.