In the short term and from where we are - yes it is a bad thing; because the censorship is mainly used to exclude true content and give lies and evil a monopoly.
But in the long term, strategically? Maybe not - because the overwhelming problem with the mass and social media is the mass and social media themselves; not the bias of their content.
99% of the damage done by the mass/ social media is irrespective of their content: even if they were only publishing true, beautiful and virtuous stuff; still the scale, pervasiveness, invasiveness and addictiveness of the media are what does most of the damage.
(Think back a couple of decades to when the internet was 'free' - were things then moving in the right direction? Obviously not.)
I personally will be sad when I am shut-down or compelled move onto a micro-medium (sending-out group e-mails, perhaps?); but the fact is that nowadays there is already so very little of the mass/ social media that interests me (and much less that benefits me), that I wouldn't much miss it too badly - indeed, it would do me good, overall.
Insofar as monitoring, control and censorship inevitably reduces usage; and insofar as once begun, censorship is likely to continue to increase exponentially... then anything which reduces the impact of the mass/ social media is probably a Good Thing.
Indeed, unless the mass/ social media collapse down to a small fraction of their current size - we really have no realistic hope.
So from where we are now, Leftist censorship is a Bad Thing - but its net effect may well be to begin to move things towards where we ought ultimately to be - which is a world without them.
(To see this argument in full, read my 2014 mini-book Addicted to Distraction)