The freedom of free software one runs on their own computer means it doesn't matter who holds the copyright to the software. If the copyright holder does something you don't like you have a copy you are free to run, inspect, modify, and share.
Remotely hosted services are a different consideration than free software (see https://www.gnu.org/philosophy/network-services-arent-free-o... for more). With remotely hosted services the user doesn't typically have a copy of the service software. So free software concerns are for the service provider. We hope the service provider runs only free software for their own sake, they deserve to control their own computers just as we deserve to control our computers.
In the particular case of free software and discussions you will publish publicly, you should consider https://www.gnu.org/software/repo-criteria-evaluation.html -- the GNU Project's ethical repo criteria. This was written well before Microsoft was known to have any interest in buying GitHub, possibly during the time when Microsoft was chastising "open source" software for existing (and still despising strongly-copylefted free software) and before their current "Microsoft [heart] open source" publicity campaign. Thus there's no chance GitHub's failing evaluation is based any ad hominem such as whether Google is somehow scarier than Microsoft.