The short answer... it depends.
The slightly longer answer, if the police properly identify themselves, no. The depends part comes down to what exactly the police are doing and if it's legal. In this instance, regardless of warrant being legal, a no-knock raid by plain clothed police is going to lean more to the self-defense side. Many states have been outlawing no-knock raids for this very reason. And really and 60 year old couple with a glock isn't a reasonable reason for a no-knock.
Self-defense against police is extremely sticky, mainly it comes down to if the person knew they were police you pretty much can't claim self-defense at all, some states have even made it completely illegal to resist in anyway... So even if the reason for the stop/arrest is found to be unlawful, non-compliance is illegal and you will be charged just with that alone. In other states, it takes pretty extreme (illegal or life threatening) actions by the police to be able to claim self-defense against them, and no-knock raids are at the top of that extreme actions list.