Does dragunity legionnaire still destroy if?

I know the legionnaire/aklys has been over asked and played out but..this is what happened:

Local Tourny match, I summon legionnaire, target aklys, equip aklys to legionnaire, opponent allows all.

I activate legionnaire's effect to destroy one of his face up monsters, he chains MST to legionnaires effect to destroy the aklys and this is when the problem starts. He argues that aklys does not activate its effect to destroy because it was not "sent" to the graveyard but "destroyed" by mst. I argued the contrary of course that aklys does still destroy a card. Who is right?

I did some research and I believe I was right and he was wrong.

Secondly I don't think that it is even possible to chain an MST to legionnaire's effect because sending the equipped dragunity is the cost of activating legionnaire's effect so by the time I activate legionnaire's effect, aklys will already have been sent to graveyard. Am I right?

Also if it is possible to chain a MST to destroy the aklys that legionnaire would send to the graveyard to activate it's effect, does legionnaire still destroy a card?