In my view, probably mintpal has its own way of judging in terms of choosing which one will Altcoin added to their exchanger without looking at the background of the coin where it originated.
They are quite selective in choosing which coins could be in they exchanger, outside the voting list of course (Mintpal added 2 Altcoin per week, 1 coin which of course we can see from the highest voted and one other decisive by Mintpal)
Not that I am siding with ISIS, but in my opinion maybe Mintpal know, that with they ​​exchanger to add ISIS will be pros and cons, and mintpal want to take advantage of it. 

It's just my Opinion.

while i dont agree with some things bittrex do either

bittrex > mintpal  

Both mintpal and bittrex have their problems, but i like mintpal better. Bittrex layout is just strange. Mintpal seemed to be better in the past and what they did today was a mistake.
Mintpal need to do what they been doing, just be more aware and work harder to fix their issues.

@ OP

Sounds like you got your knickers in a twist cause they wont list your stupid voot coin.

Mintpal definitely better and easier to use, than most exchanges, and as for Bittrex thats is the shit fest. it adds most shit coins just during the hype phaze then delists them after everyones dumped, leaving the bag holders with no where to trade.

+1000 !

I tend to watch their 'vote' page as listing of coins to avoid like the plague for that very reason.

Adding URO I can sort of understand.  I'm almost definitely sure it is a scam.  However yesterday I was completely sure it was a scam.  They're either really selling UREA or they're running the most sophisticated altcoin scam yet complete with actual business addresses, real people, etc.  A good scam would have that stuff but Mintpal is thinking: a) if this is real, it is the new Bitcoin and we'll own it b) the scammers are going to pump URO up to $300.00 dollars before fading and we'll get all of those juicy transaction fees up until the end. 

About ISIS, that just doesn't make sense.  I read their ANN when it came out:  typical scammy pump and dump meme coin (Egyptian Goddess, not the terrorists) that will get up on top of CMC for a day and then vanish never to be seen again.  Unless ISIS has something huge to release they let Mintpal on the choice makes no sense in anyway.  I'm into Voot but wouldn't have been butt hurt if Roxcoin, for example made it, or any of a bunch of other semi-non-scammy coins with a hint of innovation.

URO just makes me think of the well-known British English phrase: taking the piss

i guess they will be replaced slowly by, you should take a look at Credits CRD https://bitcointalk.org/index.php?topic=634403.0 http://vimeo.com/100148381

like craptsy was hahaha..

I must admit i was very surprised and disappointed that mint-pal  added the mostly Scam coin ISIS, it makes no sense at all.   

mint pal  should see themselves as the premier exchange and only add the best new promising coins which will hopefully be save investments for their clients. 

Bittrex is a very different  model,  Bittrex add all the latest released coin's  and basically the risk is  down to you whether their just scams  or not.

i will be moving my funds to other exchanges