If you're talking about the subway, I assume you live in Barcelona or Madrid which are large cities. Doesn't Madrid have a relatively large gay population and gay scene? In the U.S., as a rule, you need to be in a gay section of any given city to feel comfortable enough to publicly express affection like that. Otherwise, you run the risk of getting bashed. Unfortunately, Americans generally aren't as progressive or evolved as most Europeans. Once my BF and I were in the gay section of our city kissing outside a cafe. A group of girls were walking by at the time, and one yelled, "What a waste!" When we turned to look at them, my boyfriend blew them a kiss (LOL). So even if you're in a gay part of a city, you can have ignorant people passing through and making comments as well.
BTW, my BF and I have been to Barcelona. Actually my BF is originally from South America. His parents still live in Argentina. Anyhow, we had a great time in Barcelona. The people were extremely friendly and warm. I really enjoyed Las Ramblas. Actually I lived in Italy for several years when I was younger and have returned to visit several times with my BF. In Italy, you need to be in the gay section of whatever city you're in to feel safe holding hands & kissing in public. Once we were in a gay club in Bologna, and the police came to clear the bar due to a bomb threat. Yes, scary! Of course, the clubs in Milan and Rome are great fun, and you're fairly safe. Actually I've travelled quite a bit in Europe. IMO, it's alot more interesting than the U.S. Anyhow, thanks for caring.