Here's some history of Bitcoin Policy changes that were controversial at the time:
Basics: Policy is not Consensus. Satoshi's first client did not relay all transactions that were valid according to consensus. This is necessary so an attacker cannot just flood the network with zero fee (consensus valid) transactions to himself at no cost to him but high cost in bandwidth and CPU to all nodes. Still, even the the early policy filters led some to shout "censorship" when trying out things that were consensus-valid.
2013 the Dust Limit was introduced. Transactions sending 1sat to somebody were not relayed anymore. While this was a reaction to "Satoshi Dice" which permanently spammed the UTXO set with "notification transactions", it also forced other projects like "Colored Coins" back to the drawing board.
2014 OP_RETURN Data Carrier Size Limits were introduced. Before, OP_RETURN accidentally allowed spending any funds on chain which was fixed in 2010 by Satoshi, establishing the OP_RETURN as we know it today. It was limited to 40B (8175c79) and then 80B (a930658) via Policy.
2016 Replace-by-Fee (RBF) was introduced. Before that and especially in the early days, users assumed transactions to be final when they showed up in their mempool aka "wallet". "first-seen-safe" was a thing and shaking that up was perceived as an attack on Bitcoin by many. In 2016, RBF wasn't even activated for all transactions. It was an opt-in feature but still, emotions ran high.
2017 the concept of "Priority Transactions" was removed. Up until then, transactions with no fee at all were relayed and actually mined if they were "priority transactions" meaning for example to spend from old enough UTXOs.
2022 Full-RBF was introduced, enabling any unconfirmed transaction to be replaced. This somewhat revived the FUD from 2016.
2025 OP_RETURN is scheduled to be opened up to 100kB which sits at the core of the recent "Knots vs. Core" drama.
