It all depends on the situation. Legally we're entitled to use reasonable force in self defence - so if an attacker is presenting us with sufficient force, then we can retaliate with more aggressive techniques such as striking. I don't think anyone is saying that attacking and striking are necessarily wrong or bad.
Funakoshi said there is no first strike which means that a Karateka shouldn't be making the first attack. Now remember that you don't need to wait to be hit in order to defend yourself. The law defines assault as any act which makes you fear for your safety. The following scenarios also legally count as assault which would entitle you to act in self-defence:
+ Credible verbal threats. e.g. if someone says, "I'm gonna f***ing smash you!" then you can strike. They already verbally attacked your first, so your strike really isn't a "first" strike.
+ Violent/hostile/aggressive gesture or body language. e.g. if a person raises a fist at you or presents a weapon in a threatening manner then you are entitled to pre-emptively engage in self defence. Even if a person looks like they're about to throw a strike (e.g. chamber a punch) then you can strike.
...but in all of these scenarios, it's not you who's the instigator. You can pre-emptively react to an attack, but not initiate the attack - and I believe that's what Funakoshi meant by a "first strike".
Also there are many ways to _passively_ attack and strike that are less aggressive and devastating. For example, if someone is obstructing your escape path you can grapple an incoming strike and move them out of the way so that you can run away. You don't _have_ to hit them. Depends on the situation of course.
But my earlier point - and it's a point I've made before - is that teachers need to be selective in terms of what techniques they teach to who... and particularly be careful in avoiding teaching more aggressive techniques to people with an aggressive disposition (i.e. someone who's inclined to be a thug or bully). A morally responsible instructor should feel quite concerned if any of his/her students were to use techniques taught by them to go around attacking people. Unfortunately it seems that some instructors don't seem to care -- just as long as their student turns up to lessons, pays their fees and behaves at the Dojo then it's all good. They're not too concerned about their behaviour outside of the Dojo (where it matters). Some instructors are just as bad. I once met an instructor who worked as a bouncer and he was suspending from bouncing for a period of time because he had used excessive force in dealing with clients. :/
IMO people with such dispositions should NOT be taught aggressive martial arts techniques. If an instructor becomes aware that a student of theirs has such a disposition, then they should either:
+ Stop teaching them any more aggressive techniques (either solely revise techniques already learnt or just expel them - depending on the situation)
+ Teach them passive defensive techniques.
A lot of internal martial arts specialise in passive techniques, and some like Aikido almost exclusively uses defensive techniques -- Aikido has almost no attacking moves. Aikido (as well as Jujutsu) evolved from Taijutsu which was used by Samurai in situations where they were unable to draw their sword (e.g. caught by surprise or in the presence of a Lord (where drawing one's weapon was illegal and redeemable by honourable Seppuku).