There's a real tangible effect that ordinals/runes minters will face if part of the hashpower doesn't mine them in the blocks they find.
The tangible effect will be in those miners' pockets. Ordinals will get their confirmation sooner or later, whether only 50%, 5%, or even 0.5% of the hashrate mines them.
Effectively they become more expensive to be included in a block.
Nope. They become
less expensive. Let me give you an example. Group A ignores Ordinal transactions, where group B ignores no transaction. Let's assume each group owns 50% of the hashrate.
Assume we have the following mempool:
[... TXs paying less than 50 sat/vb ...]
Regular TX #1: 50 sat/vb
Regular TX #2: 75 sat/vb
Ordinal TX: 100 sat/vb
Regular TX #3: 100 sat/vb
Regular TX #4: 110 sat/vb
Regular TX #5: 120 sat/vb
For the sake of simplicity, assume that each block can have up to 4 transactions.
In the hypothetical network state, the group A would mine TX #5, #4, #3 and #2, even if #2 pays less than the Ordinal one. Therefore, it reduces the competition, because the transactions that pay less than the Ordinals have a higher chance to be mined than before. The mempool right after would be:
[... TXs paying less than 50 sat/vb ...]
Regular TX #1: 50 sat/vb
Ordinal TX: 100 sat/vb
You can see that the Ordinal now pays way more than the others, and there is still 50% chance that it will be ignored again by group A, so the Ordinal user can reduce their fee from 100 sat/vb to 51, knowing that group B would consider them with the highest priority.
If it isn't completely understandable, think of it this way: In the first mempool figure, if you were the person paying 75 sat/vb, you'd know that you have 50% chance to be picked as highest priority, whereas in the current state, you'd be completely confident that the chance would be 0%, and this would incentivize you to compete with the Ordinal user, and rise your fee rate (which would in consequence incentivize them to do so, as well).
If more miners get behind OCEAN it's indicating that they care more about what they perceive as a better step for the health of bitcoin's network rather than some short term profits
I'd argue that the health of the Bitcoin network relies on principles such as censorship-resistance being preserved at all times, no matter what. Being censorship resistant is not just game theory; it's a principle itself, just like ignoring Ordinals. I don't understand why you think that pro-censorship pools would be more ethical than anti-censorship pools.
Or at least faster than in 2013, oh wait! 
