If you're told the lie enough times, it becomes part of your reality. And if enough people are taught that lie, it becomes part of the culture.
Since the dawn of time, people (especially powerful interest groups) have used propaganda to create advantageous false beliefs among people who would otherwise be a threat to their position. Bitcoin is a severe threat to government & banks, so it is no surprise they enacted a huge campaign of propaganda to suppress & delay it. A vast array of overlapping lies, half-truths, misunderstandings & misinformation was created as part of the deliberate attack on Bitcoin which was recognised by big blockers (now BCH) in The Blocksize War. It successfully rebranded Bitcoin in the minds of the general public & created a culture on the small-block (now BTC) side which has perpetuated & reinforced this panopoly of false information. This attack was (& still is) performed through concerted censorship of the truth. Note that not everyone involved in the fallout is malicious, most are simply naive or misinformed, but a small group of malicious actors is sufficient to create a self-perpetuating flywheel of false beliefs among a much larger rabble.
A complete list of these misconceptions is nearly impossible, but a good start is the BCH vs BTC section of the Podcast FAQs. Note that this is the largest section of the FAQs, larger even than the section about Bitcoin Cash itself. This should give some indication of the scale of the problem.
Some of the most frequent recurring misconceptions or partially-valid-but-overapplied dismissals include:
- Security: BCH is lambasted as insecure due to low hashrate, which has a grain of truth but overstates the issue by ignoring almost all of the surrounding context. See Is low hashrate a problem? .
- "The market has spoken": A pithy dismissal with no logical validity. See: Hasn't BTC already won? Hasn't "the market spoken"?.
- Poor price performance: A variation of "The market has spoken" which attacks BCH's market performance without acknowledging or considering the unique circumstances involved in BCH's trading history.
- "Big blocks can't scale": A critical misconception which misunderstands Bitcoin's design & BCH's Layer 1 scaling strategy. An obsession with avoiding scaling to preserve "home nodes" is driven by aforementioned censorship & propaganda or psychology rather than engineering.
- "Bitcoin scales in layers": A misused analogy to Internet networking with no understanding of the subject matter. See: Doesn't Bitcoin scale in layers?
- Lightning Network (or other L2s) will solve or has solved scaling: An excuse to avoid discussion of L1 scaling increases, and doesn't hold up to detailed analysis. See: What about the Lightning Network?
- Hard forks = bad/centralised: Hard forks are inaccurately demonised as bad or centralised & often incorrectly conflated with chain splits. This dogma is also necessary to support "Big Blocks can't scale", "We need Lightning Network" & other nonsense.
- BCH = Just bigger blocks: BTC advocates will often claim BCH is "Just BTC with 1 number changed". Firstly, this ignores actually how much effort is involved in on-chain scaling (in node software, supporting developer libraries & tooling, wallets etc.). It implies BTC could easily replicate this, which they certainly cannot. Secondly, it's completely inaccurate as there is a very long list of differences besides blocksize between the projects, accelerating as they diverge over time.
Unplugging / reversing propaganda
The human mind is well-equipped with all manner of rationalisations & cope to protect its existing belief set, even in the face of overwhelming new evidence.
Disabusing / unplugging deeply entrenched BTC coiners is very difficult because of the large extent to which they have been programmed with a wide variety of interrelated misconceptions. Furthermore, they are likely to have entrenched social & financial investment in their previously stated positions. They also have many valid criticisms of Bitcoin Cash, so sorting through, distinguishing & addressing each true or false topic is an arduous & time consuming process.
It's very difficult to create the holistic paradigm shift necessary unless the subject is open-minded & motivated (which they often are not) to improve their own Bitcoin education - for example, by carefully reading through the Bitcoin Cash Podcast FAQs. This is a real shame, but it is a problem the BCH community has relentlessly persisted in attempting to address, despite equally relentless vilification.
The good news is that the majority of the global population are not thoroughly immersed in so many false beliefs so they come to Bitcoin (Cash) with an open mind. The most heavily propagandized BTC adopters who cannot see reason will unfortunately be harshly confronted by reality with a BCH Flippening.
See also: Why is there so much censorship in BTC?