Are there any downsides to banning node crawlers? There are multiple entities and open-source software that crawl the Bitcoin P2P network to discover and monitor nodes for various purposes (statistics, surveys, academic papers etc.)
Some of those I am aware of:

btc_node_scanner
dsn.tm.kit.edu
nodes.multiven.io
bitnodes.earn.com
bitnodes.io


Banning such nodes would free my connection slots for real useful nodes that actually provide consensus sourcing.
But, is there any downside to banning such crawler nodes?

Also, what about banning btc-seeder nodes? Would that affect negatively the health of the P2P network?



I think the ideal answer could provide the effects to two cases:

banning done by one user and how they are affected
banning done by a grand/meaningful number of users and how the overall network would be affected

Thank you
It would be hard to specifically ban crawlers as a practical matter because there is no reliable way to differentiate them from other normal nodes. They can, in fact, just be normal nodes that instrumented with code to collect the desired data and report it back to an aggregation system.
So then you are left with banning normal nodes. Since all of the value of running a node comes from its connectivity to the P2P network via other nodes, this would not make sense.