add/change,
zombieteam = "Sentry";
isgoodguy = 1;
attackpower = 0;
chance = 100;
To the datablock.
This will make it target all other bots but the sentries 100% of the time, will also prevent it from doing melee damage.
Also this needs a look animation for it to work properly.
Edit: also look at the updated Ai_national socialist code it's a little less hacky now.