Feelings run very strongly on this grave issue. Local people were always going to be watching how their MP voted. They have a right to air their views to their MP. MPs should not be surprised if they get tweets showing dissatisfaction from their constituents. They should welcome them. They are the ones who want to get people interested in politics. It's part of a healthy democracy. Attempting to silence constituents who disagree with them is unhealthy, except in the case of offensive language or threats. If there are large numbers of local people who disagree very strongly with how their MP has voted, so much so, that they may vote for another party, then it is in any party's interest to assess whether they should support that candidate in future elections. It's just logic.