Once a creature token that came under your control this turn has legally attacked, causing it to lose haste by removing Brudiclad from the battlefield won’t cause that token to stop attacking.

The last effect of Brudiclad's triggered ability affects all tokens you control other than the chosen token, including the token that was just created if that isn't the chosen token.

All other tokens you control become a copy of the chosen token, even those that aren't of the same type. For example, if you control a Treasure artifact token and choose the Myr token Brudiclad just created, your Treasure will become a copy of the Myr.

The effect of Brudiclad's triggered ability lasts indefinitely. It continues to apply after Brudiclad leaves the game.

Brudiclad copies only the values defined as the original token was created (unless that token is copying something else; see below). It doesn't copy whether that token is tapped or untapped, whether it has any counters on it or any Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, or so on.

If the chosen token is copying something else (for example, if the chosen token was previously affected by Brudiclad's triggered ability), then your tokens become copies of whatever the chosen token copied.