That sounds like the nondiscernment phrase "sin is sin." The same people say "all sin is willful."
But those are both wrong. There are sins unto death, and sins NOT unto death. Do you know the difference? Sins unto death are willful sins/lawlessness. Sins not unto death are unintentional, unknown trespasses unwittingly committed.
The sins referred to in 1 John 3 are willful sins - sins unto death. The clue to the distinction is verse 4 - lawlessness.
1 John 1:7 talks of the cleansing of sin while walking in the Spirit. Those are
trespasses, and as long as you forgive others their trespasses against you, those you commit are automatically cleansed, which leaves you constantly in a state of "sinlessness" even though you committed an unknown trespass. 1 John 2:1 has Jesus as an advocate with the Father over these sins He is constantly cleansing. This verse is NOT about willful sins unto death. The clue to this distinction is the lack of repentance required.