Let's do a experiment :

Place 3 command blocks that you'll activate in this order :

/summon armor_stand ~ ~1 ~ {Tags:["A"],Marker:1}
/entitydata @e[tag=A] {Tags:["B"]}
/execute @e[tag=B] ~ ~ ~ say test

Everything will work as expected, and the armor_stand will say "test".

Now kill the armor_stand, and change the 3rd command with this :

/execute @e[tag=B] ~ ~ ~ kill @e[r=0]

Reactivate all the command blocks.

Strangely, the armor_stand won't be killed, and "Failed to execute 'kill @e[r=0]' as Armor Stand" will appear in the command output.

Kill the armor_stand again, and just set the marker's value in the 1st command block to 0.

Reactivate all the command blocks.

Now, the armor_stand was killed...

Initially, I thought that this bug is related to MC-88533, but the basic

/summon armor_stand ~ ~1 ~ {Tags:["A"],Marker:1}

&

/execute @e[tag=A] ~ ~ ~ kill @e[r=0]

works perfectly.