How can I make my website's texts copy protected?

Copy-pasting some body else work is very common. Though, very few people actually give the credit link or mention about the sourceWell, I'll put it this way: no, there is no practical, feasible way to copy protect text on the internet. If you can see it, it can be copied.

There are lots of ways to make it more difficult. I have seen people use Javascript to turn off the copy function in the browser. I have seen people turn all of their text into an image so that you can't just copy the text, you actually have an image. But there are a raft of problems with either of those kinds of solutions and other solutions that people have proposed. Ultimately, they're all circumvent-able

You can make it difficult to copy yes, but not imposible. If someone want to steal your content there is always a way

Yes, you can't stop them from copying your content. But if you are concerned about your visibility on your search engines here is an advice for you. Always index your page in search engines as soon as it gets published. So even if someone copied the content from your website and published on their own, They won't or can't be more visible for search queries related to that specific content. Google knows where does the content belong and who should be rewarded for that.

Always index your page in search engines as soon as it gets published.

For stopping the content copy of your website you can do two things, one is to disable the mouse right click and second is to disable the cut (CTRL+X), copy (CTRL+C) and paste (CTRL+V). Using of jQuery, you can easily disable mouse right click and disable cut, copy and paste from web content.