Should blackmail be illegal?

Relevant article:

http://www.queerty.com/man-pleads-guilty-to-blackmailing-two-married-men-he-hooked-up-with-in-a-park-20150311

A man just received seven years in the slammer after pleading guilty of blackmailing two men he had anonymous sex with at a park in Worcester, England.

24-year-old Lee Taylor’s (pictured) strategy was simple: He’d hideout in the men’s bathroom at Gheluvelt Park. Another man would enter the facility. The two would have sex. Afterwards, Taylor would threaten either to reveal the men’s secrets to their families ... unless they forked over £100 ($150 U.S.).

According to court documents, the first incident occurred on November 12 of last year. Taylor met a married man in Gheluvelt Park. They did the nasty. Then Taylor requested a ride home.

“As they drove off, Taylor asked his victim for money for what had happened or he would make sure his family and his employer would know,” prosecutor Patrick Sullivan told the court.

I don't see how blackmail not being legal would do anything but make it easier on the blackmailer. The person being blackmailed would have no recourse to affect the blackmailer's behavior.
Basically his only option would be to come clean and accept the humiliation while the person extorting money from him gets off Scott free.
In my opinion, Yes, blackmail should be illegal.

Good question. It seems like blackmail should be illegal, but then again, it's not illegal to share true information with others (in most cases at least), and it's not illegal to ask others for money. Does the nature of the acts change when they are combined?

(This reminds me of prostitution: it's legal to give others money, and it's legal to have sex with others--so why should it be illegal to combine the two?)