Machiavelli on Fair-Weather Friends
Few talk about loyalty unless they are considering an act of disloyalty.
I say that nobles should be considered chiefly in two ways: either they conduct themselves in such a way that they commit themselves completely to your cause or they do not. Those who commit themselves and are not greedy should be honoured and loved; those who do not commit themselves can be analysed in two ways. They act in this manner out of fear and lack of courage, in which case you should make use of them, especially those who are wise advisers, since in prosperous times they will gain you honour and in adverse times you need not fear them. But when, cunningly and influenced by ambition, they refrain from committing themselves to you, this is a sign that they think more of themselves than of you; and the prince should be wary of such men and fear them as if they were open enemies, because they will always, in adverse times, help to bring about his downfall.
Nicolo Machiavelli from The Prince
Machiavelli's account of fair-weather friends is of course true. We all know that popularity will wane and that, when times get tough, many who declare themselves friends will look to their own interests first. Perhaps the most subtle and challenging of fair-weather friend will declare their loyalty privately while also explaining that they must avoid any undue public displays of loyalty 'for your own sake' and in order to win you support from your enemies. Such friends are effectively working as 'double-agents'.
Christ tells us to love our enemies - but He also says we should be "as innocent as doves and as wise as serpents." So any naivety about the motives of other humans - friends or enemies - is not appropriate. We must exercise responsibility to ourselves and to our affairs and watch for any threats. In particular, watch out for people who keep expressing their loyalty too often - and only in private. Few talk about loyalty unless they are considering an act of disloyalty.