The Lightning Network can take a huge amount of transactions largely offchain. The idea of having all transactions fully onchain is not a matter of principle, it's a matter of control from miners so that they can receive transaction fees more often. SegWit allows a slight increase in onchain capacity which is enough for the short term while this offchain scaling can also be implemented.
malicious spammers wont use segwit keys nor will they use lightning.
they will continue to native spam the baseblock which will still distrupt segwit keys users and lightning open/close channel operations
segwit/lightning does not solve the real problems. it just pushes innocent people away from native bitcoin with hopes and utopian dreams, but no promiss/guarantee's
The resources that spammers need to pressure the network wouldn't necessarily change very much with larger blocks. They can just send lower transaction fees for their transactions that never confirm. Higher fees mean that spam can only take the network so far as the resources needed for it rise, and therefore solutions like LN are good for there to be low fees overall due to reuse of payment channels, and low fees for larger transactions because as a percentage those fees would still be miniature.