This is a highly controversial topic.

I used to support vote-selling platforms when it first started as i saw that its a great feature that can be used to highlight great content. I no longer support them though..

It's not that vote-selling/buying is a bad thing. It's just something there to use.. But like every other problems on earth, it's how we people use it or rather abused it that turned into a shitshow it is today.

Voting a content is supposed to be an act of rewarding a creator for a content that the consumer liked.. as such ideally highly voted posts are those that people like for whatever reason. Quality is subjective but the market is the market.

Now imagine that instead of a creator creating content that their audience have to like, said creator now can literally shitpost and spam the blockchain as a placeholder, pay a vote-seller, get profit.

What is the value of the Steem token if people can pay Steem to buy more Steem? What is the value of the Steem Blockchain if Proof-of-Brain as described in the Steem Whitepaper no longer works?

It is true that a person's Steem Power represents their stake in the reward distribution voting mechanism and one can do whatever one likes with their own stake.

But I believe there should be a counter measure to make vote-selling/buying not as rampant/profitable as it is now. Perhaps a diminished return physics in place or a superlinear/sublinear reward curve instead of the linear curve we have now.

otherwise there is no reason for investors to invest in the development of the steem blockchain when their investments leaks out into the exchange almost immediately.

This is just my strong opinon loosely held.. There will be those that disagree with me, I will get some points wrong. I hope discourse can be civil if anyone feels like discussing more.

Nope, To answer your question. I don't think Vote selling is like prostitution. Because If it is anything, It is Vote selling and nothing more. You are trusting another entity to cast your vote on behalf of you and you will get the share of profit or may not. 
because if you go by that logic the SP delegation is also prostitution and your savings account in the bank which generates interest also prostitution. 

You are just putting your assets to work. Because if you are able to cast the votes by yourself by curating good contents you can make some decent returns on your time spent, And since you are not able to do it by your self you are trusting the other parties to help with it. Now it is the responsibility of the entities to take care of this trust placed in them. 
Same way like the bank take cares of their assets.

Vote selling is something whicu i do not really 

support but i will not condemn those that do it because some of them have genuine reasons 

why they sell those votes and also some steemians especially new steemians can benefit 
from the votes,i believe that the vote selling if 

done properly will not really negatively affect the 

steemit community,i think what the vote sellers 

can do is that they can make sure that they only sell votes to steemians with good content and 

content that has great values and they should basically sell votes to steemians that have not been spamming steemit..

I completely disagree with him. Selling votes is just like passive income it benefits both the seller and buyer.
Now-a-days in steemit it has become hard to come into limelight or attract people by your posts.
People comment or upvote you posts only if you have good repo( Not everyone)
In that case one buy votes until he gets 50 to 60 rep or even after that.
Moreover everyone wants the longterm benefits and thats why we are working hard on steemit. 
There might be a situation where you can't make daily posts but your steempower is high. I'll bet that no one want their hard work go in vain. They could sell their votes and earn from them.
Mentioning selling votes as prostitution is absurd. Smartwork and illegal work are entirely different.