The thing that bothers me with altering isn't whether or not people choose to do it. If you make an informed decision for no matter the reason be it convenience, precaution, heck even looks I'm ok with it. Because it was informed.
I'm not ok with lying or withholding truth or exaggerating things so that the general public will just get their dogs altered because we obviously can't trust them. Just no. I am not ok with people getting told they should alter their animals or they will die of cancer after having a million babies, peeing on everything and eating your children. Stop with the lies. Educate people! Especially when it's people that obviously care enough they go to their vet or trainer or someone they trust only to get told the propaganda fear mongering because they've been deemed too stupid to handle the truth.
Yes, the average person I meet has no clue what a heat looks like, they think when the dogs stop bleeding it means it's over. But, how many of the places that love to scream the dangers of intactness take a moment to say "Ok, but if you do keep your dog intact here are the things you need to watch out for and protect against."
It's basically the same problem I have with abstinence only teaching. Sure, most teenagers are morons but still give them the tools and knowledge to make an informed decision and do it safely.
ETA: On docking and cropping I really have no opinion. I don't care if people do it, I wouldn't want to take the choice away from them but it doesn't bother me if it slowly dies off.