Why should the law care about what I do behind closed doors?

The law shouldn't care (if you are a law abiding citizen) about who you take into the bedroom as long as they are consenting adults. How many guns you own. What you eat for supper. What kind of TV shows you watch. Whether you watch porn or not.

You can stand on a public sidewalk and take pictures of my house. You can't walk into my house uninvited and start taking pictures.

The law doesn't care about what you do behind closed doors as long as it is within the bounds of what the law allows.

Trump is going to target known criminals in the country illegally for deportation. The Democrats have vowed to fight him every step of the way. Don't they understand this is one of the issues that cost them the white house, the house and senate?

But what if you're raping little girls behind closed doors? Killing gay men? Watching child porn?

It shouldn't to a point.

If evidence arises that you are doing these things behind closed doors, don't you think the government has a moral obligation to investigate?

Why are Republican politicians so afraid to oppose Trump?

Liberty is not boundless. It does have its limits.

Society sets laws announcing those actions that it deems unacceptable in polite society. If evidence appears that causes a reasonable person to suspect that illegal activity is going on, society should investigate. Of course society might find itself having to jump through hoops by adhering to constitutional law. It cannot just invade your personal space and demand to know what you're up to just because they don't like you.

Your speech is free. But if it causes malicious harm to someone, you can be sued.

How does it feel to have sex with a 40 year old curvy aunty?