Given that your experience is not a common occurrence, I feel safe saying that you cannot simply conclude that calibre is in general a dangerous application to install.
Something about your setup is different from other peoples' setup.
You said someone else has the same problem, but didn't post a link to where they said it... so I won't comment about their experience.
...
Granted, you certainly aren't being forced to use calibre.
And actually, if you don't know what interaction caused the problem in the first place, then simply reinstalling will probably not fix everything magically either.
For now, just see if using a different user works okay, if so then something in your settings got corrupted which is a much easier thing to fix.
You can revisit the question of whether to attempt to use calibre again, after you know more about what happened and how to fix it.