I would heavily suggest reading further into this issue before voicing strong opinions. Upon further research, taking me literally 5-10 minutes, I found that the reasons for the detainment of these two individuals was due to denial of entry into the country. Thus, they are detained and refused entry into England until they can/will be sent back to the locations from which they departed.

The reasons for their denial of entry, if people are interested, is due to suspicion of travelling to the country to push extremist views and potentially incite hatred (which could turn violent). In large parts of Europe, there are laws to hinder harmful or violent racial/cultural discrimination. Frankly my sources are in Norwegian so they will be pointless to link you, but I can post the meaningful quotes they gathered (in English) from their British sources.

"On Friday night, Martin Sellner, the Co-Leader of Generation Identity Austria, was refused entry to the UK at Luton Airport. After landing at approximately 13:00, he was detained by Border Police and separated from US Vlogger, Brittany Pettibone. He was subsequently informed that he was being denied entry to the UK and that he would be detained until Sunday evening when he would be allowed to return home."

So in other words, they are not being "jailed" or "imprisoned" for their wish to speak about an issue, but are rather being denied entry into the country for this specific purpose only. From what I could also quickly gather, Martin Sellner specifically is strongly anti-islam, having been involved in neo-nazism in his earlier life, as well as now being a prominent figure in nationalist, so-called "anti-sharia" groups. And while I don't disagree with criticism of religions or cultures, inciting hatred for them is something entirely different.

Whether or not their speeches legitimately would incite hatred and/or violence however is something I am uncertain of, as none of the websites I have found would give any valuable level of context as to the specifics of these supposedly harmful speeches. Please keep in mind, the 2 articles linked by Synthic above are both far-right and thus prone to heavy bias. Both articles fail to mention the fact the primary action here was denial of entry, making this issue out to be far worse than it really is. And to be as transparent as I can, the Norwegian sources I used were in fact also right-leaning, but simply provided more valuable information.

Lauren Southern has revealed, that after speaking with Brittany Pettibone on the phone, the police have detained the couple separately and for the ‘crime’ of having right-wing opinions as well as wanting to interview Tommy Robinson and holding their speech.

HAHAHAHA I CANT EVEN, these memes dude.

Where was that quote from? And what makes it a meme?

I'm guessing that site has something to do with it?

This Weiner measuring contest needs to end...

It’s a meme because Lauren Southern and Tommy Robinson are despised by left-wing media.