LSE socially disaster?

A friend of mine advised me to not go to LSE, because it is full of arrogant and cliquey people. He said that when you go to LSE, you feel like you are in high school because people only make friends with either people from their own program or their own nationality, they are not open to anything else. I took his opinion with caution and would like to know wat other people think about the social life at LSE? Is it really toxic? And should this putting me off to go there. And what is the social life at UCL and KCL?
I couldn't decide me between Environment and Development at LSE, Environment, Politics and Development at KCL and Environment, Politics and Society at UCL. Which university is in term of social life the best one?

I did my graduate at LSE and my undergraduate at UCL. In terms of diversity, I found LSE very disappointing. In my cohort 65% were from one country (China) and the rest were from USA, Colombia, Japan, India, France and Germany. And everyone has it's own group (there were at least 2 from any nationality). I was the only person who was single presented in terms of nationality. And that made my social life at LSE horrible. It was very hard to find friends, because every nationality only hanged out with their own. At UCL my experience was the opposite, everyone was very open-minded to befriend with another and also the diversity was better. Also the halls at UCL were better in terms of social life than at LSE. I agree, that most people at LSE only hang out with people from their own program, while at UCL I also could get in touch with people from different programs. Also I found the chance to meet people from all over the world is at UCL higher. I met people from Barbados, Australia, Egypt, Saudi-Arabia, Brazil, USA, South Africa, UK, Ireland, Spain, Cyprus, China, UAE, India, Pakistan, South Korea and more at UCL, while at LSE I mostly met people from China and USA, and India, with some people from Colombia, Japan, France and Germany. In terms of social life and diversity and international network I will go any time for UCL. The only thing that I found at LSE better is the library. I enjoy my time at UCL a lot, while at LSE, I feel me very alienated.