Unfortunately, it is almost impossible to use this tactic to advocate in favor of something (rather than against it).
I wish I had a suggestion for how to parry the accusation, but I don't.
Without a law like this, we're just going to keep fighting the same battle every 4-6 years. They only have to win once, we have to win every time. It's not a fair fight.
I happen to believe that it was protected by the first, fourth, and ninth amendments, but I am not sure it is possible to erect permanent legal bulwarks against ever-expanding federal powers. As an example, the second amendment specifically enumerates gun rights, yet it is under constant assault. The only way I can see to protect this type of individual liberty would be to radically de-scope the federal government, but I don't think that's going to happen.
Again, I really wish I could be more optimistic, but I just don't see any realistic hope.
Think of the LGBT children who may want to speak to a safe and established community / therapist confidentially about problems in an abusive household which rejects them for what they are.
Think about all the children who may need counselling during the COVID-19 outbreak who do not need secrecy from family but can't physically attend and don't want strangers peeking in.
"Think of the children that want to embrace $RELIGION but happen to live in a den of $DEITYless liberals."
"Think of the children afraid to express conservative views online because of a lack of privacy protections."
The fact of the matter is some parties (by which I mean groups, not political parties) have an abiding interest in keeping strong encryption and privacy out of the hands of the population at large. Banning E2E encryption either outright, or through the backdoor (EARN IT act) from major Internet platforms will accomplish this. Therefore, arguments like "You can't ban math" or "The real criminals will just move to platforms that use E2E encryption" don't work.
What's worse, they try and pass these laws using Think of the Children[1]. It's tested, and effective. It works because it's an emotional appeal and most voters are emotional creatures (including me, and you). Like a popular Internet meme says "You can't reason someone out of an opinion they didn't reason themselves into."
Fortunately we can (honestly) use Think of the Children to fight back. Literally every child in the US uses the Internet to chat with their friends and send pictures, write their journal, do their homework, get their grades, and communicate with their doctors or therapists. Weakening encryption therefore endangers every child, risking exposing their innermost thoughts and conversations to the worst sort of people online.
We have to start couching this issue in terms that regular people understand.
"Would you lock your backyard gate, where your children play, with a TSA lock?"
"What if your pediatrician's office told you their doors and file cabinets have a TSA lock on them? Anyone can just buy a key on Amazon, walk in, and rifle through everything they have."
I honestly worry about a future where my children have no privacy. Where any online predator can potentially access everything they say, send, post, or do online. That makes me anxious and frankly, a little angry.
1. https://en.wikipedia.org/wiki/Think_of_the_children