If you didn't mine the block, you are going to validate it. If a malicious miner starts deploying quadratic intensive blocks at higher MB (e.g. 2 MB), they could make you constantly be behind them (hence DDOS).
now your starting to see why segwit hasnt fixed it!!
There is no risk at 1 MB, and with >1MB for Segwit you'd have linear time so it has been fixed in this context.
your still thinking from the HOPE of a 2merkle soft activation where people move to segwit tx's..
your question was
"If a malicious miner starts deploying quadratic intensive blocks at higher MB (e.g. 2 MB), they could make you constantly be behind them (hence DDOS)."
stop flip flopping to hide the risks of a 1 merkle segwit, by then round circling back to a 2 merkle*.
stop flip flopping to hide the non-fixes of a 2 merkle segwit, by then round circling back to a 1 merkle.
by lowering the txsigops (not fake the maths) you can both allow more tx's in and reduce the CPU demand of native tx's no matter if people are using segwit or not
P.S
*you forget to remind yourself that segwit linear time is ONLY IF people move to segwit keys (which malicious pools/spam users wont do) so stop trying to assume segwit will help, because pools/users that want to be malicious wont use segwit keys