Data on Twitter that shows how unrepresentative it is of the general population
Twitter is a popular source for the media of public comment and the sentiments on it are taken as being representative of public opinion. In reality, Twitter is very unrepresentative of actual public opinion. This is a factor that should always be considered when assessing things from what you see on the site, and held against those who would use Twitter to support their position in disagreement with us.
The data shows Twitter's userbase to lean heavily left.
A Pew survey from 2019 found the following:
Twitter users were more likely to identify as Democrats, and probably more tellingly, tended to be younger, more highly educated, and wealthier than the general public, all things that point to the platform being dominated by a large, progressive/left-wing activist class.
Studies from the UK find the same there. It's fair to say it's a common bias in the West, particularly in the English-speaking world.
Taking a finer look at these platforms I think would reveal an even greater bias in the userbase. You could look at the popularity of hashtags or the prominent voice of certain particularly left-leaning demographics. The above data is all I have for now though.