Why some people hate Ubuntu?
Because like all people, techies also like drama.
Ubuntu is a great distro. It's stable and up to date, embeds some non-free firmwares that make it work out of the box on many systems, has a big community... Canonical, the company behind it, actually pays people to work on free software, they also push computer manufacturers to deliver Ubuntu instead of windows.
The thing is its a commerical company that aims to make profit. Unlike redhat, which is focused on business with companies, ubuntu is focus on consumers. Companies are being seen as evil by the FOSS enthusiasts so if you make them pay for FOSS its OK, but consumers are seen differently.
Why I shouln't use Ubuntu if I care to secure and privacy at same time?
Some people are selectively paranoid. Ubuntu did some controversial things but they stepped back. If you care about privacy and you are using Ubuntu, keep using Ubuntu and focus on something else. Don't waste your time with this drama, you won't improve your privacy by changing your distro.