Calling them travellers and/or gypsies (I know they are technically different groups of people but generally the terms are often used interchangeably) is not in itself a slur.

It's not a slur, but naming them in an online discussion usually provokes an unproductive shitfight about whether they're as bad as their reputation.

But almost anyone who lives in the UK would know who you were referring to. So you are just using a euphemism, which is arguably worse.

And ostentatiously not naming them has a similar effect. You could have just said "people".