Well on this topic alone the fear that many have is that should this law be passed then cases of discrimination would be raised in the ECHR. I have already read of gay people keen to push for this the second "gay marriage" is introduced.
I personally believe it is naive to believe that should "gay marriage" be introduced the gay lobby would stop at that point. I have heard Peter Tatchell himself state that this would be the next step.
As I've said so many times now, I am of the opinion churches should not be forced to marry.
I agree with your first paragraph. There will be a vocal minority who will use ECHR to push for that. I am strongly against that. I am hoping common sense and respect prevails. I said practically the same thing a few pages back.
I dislike Peter Tatchell. However, I have heard him saying the opposite on BBC Big Questions. Saying he doesn't want churches to be forced. Could you say where you heard this please?