It can be the case. But I think genuinely it probably depends on the people moving in.
Try to look at it the way that many local people might see it... Imagine you've been born and raised somewhere where you know everybody and are related to lots of people. Your culture is quite different to most of the UK (even non-Highland Scotland). I'm not talking about 'kitsch' culture, but everyday culture, like a different sense of humour, walking into people's homes without knocking, being really laid back so that you take a year to get round to the job you said you'd do, going above and beyond to help random neighbours etc etc. There are lots and lots of small things like this that are different in the Highlands. I didn't realise they weren't standard until I lived away for a while in my early twenties! That was a shock!
Now imagine this place you're from being flooded by people from outside it moving in. At first you're really not bothered; a few people can't change the local dynamic and it's nice to see new faces. But they don't quite fit in; they appear to on the surface - everyone is polite etc. But they don't quite get the sense of humour, so you have to tiptoe around them a bit or they're offended. They are horrified when the electrician/plumber they've booked doesn't turn up for weeks and get all shouty and demanding. They lock all their doors and windows and cars and generally think someone might steal their stuff. They will help out neighbours, but only if it doesn't inconvenience them too much and only if there's a sort of fair helping-out trade (generalisation I know).
When there are one or two people in a village who are from a different culture (and rest-of-UK is a different culture, no matter how it appears on the outside) it doesn't really matter. But when they come in droves, there's enough of them to change the social dynamic. And then, your generations-old locals see their culture changing and being eroded before their eyes. And the 'incomers' don't even realise they've done it, because they don't see the under-the-surface culture which is there. It makes local people sad.
My point is, by all means move to the Highlands. BUT be aware that you are contributing to the erosion of this subtle Highland culture, and tread lightly. If your plumber doesn't turn up, just leave a friendly reminder message. If people walk into your house, don't mind it. If people don't necessarily invite you into their friendship groups, they might not be deliberately excluding you; they might just have a gang of friends that they've spent all their lives with and they are quite happy. They just might not particularly want to work hard to include someone who might not quite get their sense of humour and to whom they are going to have to explain cultural references for years because there are so many, and who is going to continue pronouncing all the placenames wrong despite their best efforts.
I hope I've explained that okay. I am not anti-incomer, but there are definitely good ones and bad ones!
There are some more practical considerations too...
First, consider housing. You might move from a place like a city/town, where you've been able to get a well-paying job (by which I mean more than £25k). You've therefore built up a good stash of money / bought a house. You then decide to move to the Highlands, where local people often have low-paying jobs (min wage) and where, historically, house prices were in line with this poor job market. No longer the case. Incomers have greater buying power and can often therefore outbid locals. You might have bought the house that two local families also put an offer in on, but they couldn't match the wealth that you've built up coming from a place with better job opportunities. Maybe one of their grandparents originally built the house and it has great sentimental value. You have a legal right to buy it, but be sensitive to the fact that others might have wanted it. Don't bang on about it.
Second, people don't flash wealth here. It's distasteful, so don't do that. Flashy cars are the preserve of the occasional young idiot who's just passed his test.
Third, directly related to your B&B dream! You might want to consider that if this is the only way you intend to earn money, you won't integrate very well. The non-locals who fit into the community best long-term are the ones who move in pre-retirement and get local jobs, so people get to know them. The Co-op is great for this! Everyone will see you there :) There's usually plenty of seasonal work in the Highlands, so if you get a job in the Co-op or somewhere tourist-based, you won't be considered as 'taking a local's job'. I've never really heard anyone talking about incomers taking jobs anyway; it's more the housing people focus on.
I hope it helps - genuinely trying to be helpful, not negative :)