Instead of using their considerable intelligence for the promotion of peace, as do Vulcans, Romulans are bellicose and at perpetual war with the Federation (an interplanetary organization that includes humanity).
The Romulans are notorious for being able to “cloak” their ships with a device that renders them invisible. This makes for dramatic battle scenes similar to the contemporary naval destroyer and submarine.
The creators of the original Star Trek chose the name Romulans to resemble Romans, which subconsciously resonates with ideas of power, military intelligence and forceful acquisition.
As screenwriter Paul Schneider says:
In a humorous vein, Romulan ale is a blue, illegal drink that many Federation officers mention during moments of lively banter.
In this image (immediately right) we see a Romulan Commander whom Captain Kirk seduces in order to gain freedom from captivity. When she finds out their mutual affection was a ruse on the part of Kirk, she’s hurt and he feels a bit badly.
Interspecies love is no big deal in the Star Trek universe. People with a true eye as to what sci-fi is all about tend to be less concerned about things like gender, age, sexual orientation and race.
However, some sci-fi buffs still seem to be hung up on these conventional categories. Maybe they like to fantasize about a better world but are not mature enough to put their fantasies into reality.
¹ See https://en.wikipedia.org/wiki/Romulan This reminds me of an arrogant man I once knew who felt that North Americans lacked “culture.” He (somehow) physically escaped the grip of his communist country to benefit from living in our free society. But ideologically, he was still imprisoned. He had no appreciation, other than his visible excitement at the mere mention of scanners and computers, for the depth and innovation of North American culture.
² Read my notes for more: http://marker.to/anwBFm