The young actors are clearly not a threat to Canada in any way, and there is no rational reason for denying them entry that has been given by the government.  If the government genuinely believes that they would apply for asylum in Canada, they must also believe that there is a good reason that they would need asylum, and should consider granting it on that basis. 
I have seen the government repeatedly deny visitors' visas to Cubans as well over the years, again with no valid reason except perhaps to please the Americans. Yet they allow many more undesirable people entry because they happen to be born in the right country. Time to stop this disgraceful discrimination.